Peter Abelard: The Life, Philosophy, and Theology of a Medieval Pioneer

Peter Abelard (1079–1142), often referred to as Abailard or Abaelard, stands as a towering figure of the 12th century, a period of intellectual and cultural resurgence in Europe. A philosopher, theologian, poet, and musician of immense talent, Abelard was the leading intellectual of his generation. Before the widespread rediscovery of Aristotle’s works, he elevated the native Latin philosophical tradition to unprecedented heights. His brilliance was undeniable, marking him as arguably the most significant logician of the Middle Ages and a pivotal figure in the development of nominalist philosophy.

Abelard fearlessly championed the use of reason in exploring matters of faith, notably being the first to employ the term “theology” in its modern sense. His systematic investigations into religious doctrines were characterized by profound philosophical insight, intellectual rigor, and a boldness that challenged traditional thought. To his contemporaries, Abelard was larger than life. His legendary wit, sharp intellect, exceptional memory, and pronounced self-confidence rendered him a formidable debater, reputed to be undefeated in argument by both admirers and detractors. His powerful personality left a lasting impression on everyone he encountered.

His tragic love affair with Héloïse transformed him into a romantic figure, while his intellectual clashes with Bernard of Clairvaux over the roles of reason and faith positioned him as a precursor to the Enlightenment. Yet, despite the drama of his life, Abelard’s enduring fame rests on his philosophical achievements, which remain a cornerstone of Western intellectual history.

1. Life and Works of Peter Abelard

1.1 The Tumultuous Life of Abelard

Peter Abelard’s biography is remarkably well-documented. Beyond the official records of his time, his personal life is vividly revealed through his autobiographical work, Historia calamitatum (“The Story of My Troubles”), and his poignant correspondence with Héloïse. These writings offer an intimate glimpse into the inner world of this complex figure.

Born around 1079 into a noble family of minor standing in Le Pallet, Brittany, near Nantes, Peter Abelard showed an early aptitude for learning. His writings reveal a deep familiarity with classical authors such as Cicero, Horace, Juvenal, Ovid, Lucan, Seneca, and Virgil, indicating a robust early education in classical literature. Rejecting his inheritance and the prospect of knighthood, Abelard dedicated himself to philosophy, traveling to study under renowned thinkers like Roscelin and William of Champeaux.

In the early 12th century, Abelard’s confidence in his intellectual abilities grew, and he began his career as a lecturer, initially in Melun and later in Corbeil. He directly competed with William of Champeaux, a prominent figure in Paris, for students and academic prestige. However, the intense pressure took a toll on Abelard’s health, and he was forced to retreat to Brittany for several years to recover.

Abelard returned to Paris between 1108 and 1113, revitalized and ambitious. He resumed attending William of Champeaux’s lectures, engaging his former teacher in debates, particularly on the problem of universals. Abelard claimed to have surpassed William in these intellectual contests, establishing his reputation as a formidable dialectician and securing teaching positions in various schools. Around 1113, driven by intellectual curiosity, Abelard turned his attention to theology, seeking out Anselm of Laon, the most esteemed theologian of the time (distinct from Anselm of Canterbury). This mentorship proved disappointing. Anselm’s traditional pedagogical methods clashed with Abelard’s innovative and critical approach. After a period of intellectual disagreement, Abelard returned to Paris to pursue his theological studies independently, marking the end of his formal ученичество.

Upon his return to Paris, Abelard attained the prestigious position of scholar-in-residence at Notre Dame. This period of academic success was dramatically disrupted by his passionate relationship with Héloïse. The ensuing scandal led to Abelard’s castration at the hands of Héloïse’s enraged relatives. Following this traumatic event, Abelard entered the Benedictine monastery of Saint Denis, and Héloïse became a nun at the convent of Argenteuil.

After recovering from his injuries, Abelard resumed teaching at a nearby priory, focusing on theology, especially the doctrine of the Trinity. His method of philosophical analysis was perceived as a radical departure from traditional theological approaches. A synod convened in Soissons to scrutinize Abelard’s theological writings condemned his work and compelled him to publicly affirm his faith—an experience he considered deeply humiliating. Shortly thereafter, he sought solitude in a remote and uninhabited area, aiming to dedicate himself to contemplation.

However, circumstances intervened. Abelard recounted that financial necessity compelled him to return to teaching. Students flocked to him in large numbers, and together they established an oratory named the Paraclete. Here, Abelard continued his prolific writing, teaching, and scholarly pursuits. This period of relative tranquility ended around 1126 when Abelard accepted an invitation to become abbot of the monastery of Saint Gildas de Rhuys in Brittany. Soon after, he transferred the Paraclete to Héloïse and her fellow nuns, whose convent had been confiscated.

Abelard’s tenure at Saint Gildas proved tumultuous. He found the monks resistant, obstructive, and even dangerous. He claimed to have faced multiple assassination attempts during his time there. It was during this difficult period that he penned the Historia calamitatum and initiated his famous correspondence with Héloïse, reflecting on his past and grappling with his present challenges.

By the mid-1130s, Abelard received permission to return to Paris (retaining his title of abbot) and to teach in the schools on Mont Ste.-Genevieve. It was during this period that Bernard of Clairvaux became aware of Abelard’s theological treatises and raised objections to both their content and Abelard’s rationalistic approach to faith. After initial attempts to resolve their differences proved inconclusive, Abelard requested a public debate with Bernard, scheduled for June 3, 1140, in Sens, to settle their theological disagreements. Bernard initially declined, arguing against debating matters of faith, but later accepted. Unbeknownst to Abelard, Bernard orchestrated a separate commission to examine Abelard’s works under suspicion of heresy.

Upon discovering that the event was not a debate but a pre-determined condemnation, Abelard refused to participate, declaring his intention to appeal directly to the Pope. He left the proceedings and began his journey to Rome. The Council, nonetheless, condemned nineteen propositions purportedly found in his writings and adjourned. Bernard launched a successful campaign, petitioning the Papal Court before Abelard even left France. A papal letter upholding the Council of Soissons’s condemnation reached Abelard at Cluny, ordering him to silence.

By all accounts, Abelard immediately complied and even reconciled peacefully with Bernard. Peter the Venerable, the abbot of Cluny, interceded on Abelard’s behalf with the Pope, who subsequently lifted the sentence. Abelard remained under Peter the Venerable’s protection, first at Cluny and then at St. Marcel, as his health gradually declined. Peter Abelard died on April 21, 1142. His remains were interred at the Paraclete and are now, alongside Héloïse, in the Père Lachaise cemetery in Paris, a testament to their enduring, intertwined legacy.

Abelard’s influence extended far beyond his lifetime. His students rose to positions of power and influence as kings, philosophers, poets, politicians, theologians, and monks, including three popes and numerous heads of state. While explicit references to Abelard’s thought are less frequent in the later Middle Ages, likely due to the cloud of the Soissons condemnation, his impact on 12th-century philosophy and potentially on 14th-century intellectual developments is undeniable.

1.2 The Diverse Works of Peter Abelard

Pinpointing the exact dates of composition and even the complete count of Peter Abelard’s works remains a challenge for scholars, sparking ongoing debate. This complexity arises from Abelard’s constant revision and rewriting of his texts, resulting in multiple versions of the same work circulating. Additionally, some of his writings may represent evolving teaching notes from his courses and seminars. Consequently, the notion of a fixed “date of composition” becomes somewhat blurred when applied to Abelard’s extensive body of work. Aside from his correspondence, which can be dated with reasonable accuracy, Abelard’s surviving works fall into three main categories: dialectic, ethics, and philosophical theology.

The first category comprises Abelard’s works on dialectic, encompassing logic, philosophy of language, metaphysics, and philosophy of mind. His two magnum opuses in this area are:

Logica ‘ingredientibus’ (“Logic for Beginners”), starting with the words ‘To those beginning…’
Dialectica (“Dialectic”)

These works follow the structure of the logica vetus, the “old logic” inherited from antiquity, which included Porphyry’s Isagoge (an introduction to Aristotle), Aristotle’s Categories and On Interpretation, and Boethius’s introductions and commentaries on Aristotle’s logic. Abelard’s dialectical works engage with the material presented in the old logic, albeit in distinct ways. Logica ‘ingredientibus’ offers a detailed textual commentary on the old logic, although only portions have survived, specifically commentaries on the Isagoge, Categories, On Interpretation, and On Topical Differences. Dialectica, in contrast, is an independent treatise on dialectic that treats the same material thematically. Regrettably, the beginning (covering the Isagoge and the start of the Categories) and the end (on division and definition) of Dialectica are lost. In addition to these major works, Abelard penned four lesser works on dialectic:

Introductiones parvulorum (“Logic for Beginners”)
Logica ‘nostrorum petitioni sociorum’ (“Logic at the Request of Our Companions”), starting with the words ‘At the request of our friends…’
Tractatus de intellectibus (“A Treatise on Understandings”)
Sententiae secundum Magistrum Petrum (“Master Peter’s Views”)

Introductiones parvulorum is a series of elementary commentaries on the old logic, again incomplete in its preservation. Its simplified level has led some scholars to suggest it originates from Abelard’s early career, while others dispute its authenticity altogether. Logica ‘nostrorum petitioni sociorum’ appears to be a work in progress. It presupposes familiarity with Abelard’s earlier Logica ‘ingredientibus’ and explores advanced topics not covered there. However, significant portions also serve as a straightforward paraphrase or commentary on Porphyry’s Isagoge. It exhibits textual parallels with other Abelardian works and demonstrates some theological awareness. Tractatus de intellectibus examines concepts or “understandings” from both logical (as providing term meanings) and philosophical of mind (as vehicles for mental content) perspectives. Sententiae secundum Magistrum Petrum may be a record of Abelard’s lectures, focusing on logical and metaphysical puzzles related to wholes and parts.

The second category encompasses Abelard’s writings on ethics:

Ethica seu Scito teipsum (“Ethics, or Know Thyself”)
Collationes (“Conversations”), also known as Dialogus inter Philosophum, Iudaeum, et Christianum (“Dialogue Between a Philosopher, a Jew, and a Christian”)

Ethics provides an analysis of moral worth and the appropriate degree of praise or blame for agents and their actions, though it abruptly ends at the beginning of its second book. Conversations presents a series of debates (among characters appearing to Abelard in a dream) on the nature of happiness and the supreme good. The Philosopher, representing natural reason, first debates with the Jew, representing the Old Law, and then with the Christian, who defends Christian ethics from a philosophical standpoint. Abelard also composed a short work of practical advice for his son, Astralabe:

Carmen ad Astralabium (“Poem for Astralabe”)

This work offers moral guidance and edifying sentiments in a series of distichs.

The third category includes Abelard’s works of philosophical theology. His three main theological works are dedicated to a philosophical analysis of the Trinity, with multiple versions reflecting the evolution of his thought and his attempts to align with orthodoxy (each work underwent several revisions):

Theologia ‘summi boni’ (“Theology of the Highest Good”), beginning with ‘The highest good…’
Theologia christiana (“Christian Theology”)
Theologia ‘scholarium’ (“Theology for Students”), beginning with ‘In the schools…’

The first version of Theology appears to be the work condemned at the Council of Soissons, while the last was condemned at the Council of Sens. Besides these thematic treatises on philosophical theology, Abelard also wrote several commentaries:

Expositio orationis dominicae (“Exposition of the Lord’s Prayer”)
Expositio symboli Apostolorum (“Exposition of the Apostles’ Creed”)
Expositio fidei in symbolum Athanasii (“Exposition of the Faith in the Athanasian Creed”)
Hexaëmeron (“Commentary on Genesis 1–2:25”)
Commentaria in Epistolam Pauli ad Romanos (“Commentary on St. Paul’s Letter to the Romans”)

The first three commentaries are brief. However, Abelard’s discussions of the opening verses of Genesis and Paul’s Letter to the Romans are extensive and detailed (the latter is also relevant to his ethical theory). Abelard also addressed questions of faith and reason in a short work:

Soliloquium (“Soliloquy”)

This brief internal dialogue, modeled after Augustine’s Soliloquies, features “Peter” in conversation with “Abelard.” More practical theological questions were raised by Héloïse in a series of inquiries on behalf of herself and the nuns of the Paraclete:

Problemata Heloïssae cum Petri Abaelardi solutionibus (“Héloïse’s Questions with Peter Abelard’s Solutions”)

Practical matters are also addressed in Abelard’s sermons, hymns, and lamentations (planctus). Finally, Abelard composed an immensely influential theological work devoid of theoretical speculation:

Sic et non (“Yes and No”)

In Sic et non, Abelard compiles 158 questions, each accompanied by patristic citations that suggest a positive answer (sic) and others implying a negative answer (non). Abelard does not attempt to reconcile these apparent contradictions but, in his preface, lays out principles for proper hermeneutical investigation: identifying ambiguity, examining context, making relevant distinctions, and so on.

Abelard’s students and disciples also recorded many of his views, although this material remains largely unexplored. References within Abelard’s extant works hint at other writings now lost: Grammatica (“Grammar”), Rhetorica (“Rhetoric”), a commentary on Ezekiel from his early theological studies, and others. It is possible some of these works may yet be rediscovered.

2. Metaphysics: The Nominalism of Peter Abelard

Abelard’s metaphysics represents the first significant articulation of nominalism in Western philosophy. While his assertion that universals are merely words (nomina) justifies the nominalist label, a broader irrealism better characterizes his metaphysical stance. He adopted an irrealist position not only regarding universals but also propositions, events, times beyond the present, natural kinds, relations, wholes, absolute space, hylomorphic composites, and similar abstract entities. Instead, Abelard championed the concrete individual, in its full complexity and richness, as sufficient to populate reality. He favored reductive, atomistic, and material explanations whenever feasible, actively challenging the metaphysical excesses of his predecessors and contemporaries.

Abelard defended his claim that universals are simply words by arguing for the incoherence of ontological realism about universals. Specifically, he contended that no real entity could satisfy Boethius’s criteria for a universal—something present wholly in many at once, constituting their substance (i.e., defining what an individual is). Therefore, Abelard concluded, universality is not an ontological feature of the world but a semantic characteristic of language.

Consider the realist position: universals are things in the world. If the universal animal is a single entity fully present in both Socrates and a donkey simultaneously, making each entirely an animal, Abelard pointed out a contradiction. The same entity, animal, would be simultaneously rational (due to its role in constituting human being) and irrational (due to its role in constituting donkey). This would mean contraries existing simultaneously in the same thing as a whole, a logical impossibility.

To the realist counter-argument that rationality and irrationality are not actually present in the same thing, Abelard offered a two-pronged response. First, he rejected the notion that they are only potentially present. Each species is actually informed by a contrary, and the genus is actually present in each species as a whole. Consequently, the genus is actually informed by one contrary in one species and the opposing contrary in another. Since the genus is entirely the same in each, it is therefore actually informed by contradictory properties, leading to the contradiction.

Second, Abelard aimed to demonstrate that contradictions would arise not just in the genus but even within a single individual. Socrates is (an) animal, and Brunellus the donkey is also (an) animal. By transitivity, if each is wholly and completely animal, then Socrates is Brunellus, making Socrates both rational and irrational. Put another way, each is essentially an animal, and furthermore, essentially rational and essentially irrational.

If one objects to this line of reasoning, arguing that individuals are unique due to their non-essential features, Abelard countered that this “makes accidents prior to substance.” This objection, he argued, mistakenly claims that individual things are individuated by features that contingently characterize them, confusing things with their accidental properties.

Realism fares no better if universals are identified with collections of things. Abelard argued that collections are dependent on their parts and, furthermore, a collection is not shared among its parts in the way a universal is said to be common to many. Identifying the universal with the individual in some way, for example, by claiming Socrates qua human is the universal human being, also fails. Abelard reasoned that if the universal is truly the individual, then either individuals like Socrates must be common to many, or there must be as many universals as individuals, both of which are absurd.

Abelard concluded that universality is purely linguistic, not an ontological feature of the world. More precisely, he held that common nouns (like ‘animal’), verbs, and negative names (like ‘not-Socrates’) are correctly predicated of many and thus qualify as universals. These terms are semantically general, meaning their sense applies to more than one thing, but they do not name a general entity. Instead, they distributively refer to each of the individuals to which the term applies. For example, the term ‘animal’ has the sense living substance, which is inherently general, and it refers to each individual animal because each is a living substance—or, as Abelard put it, because each has the status of being a living substance. This shift from ontology to semantics is further explored in Abelard’s philosophy of language.

Abelard maintained that everything in the world, except for God and angels, is either form, matter, or a composite of form and matter. Matter is what something is made of, whether it persists in the final product (like bricks in a house) or is transformed (like flour in bread). Ultimately, all material objects are composed of the four elements: earth, air, fire, and water, though these elemental forms are often altered in combinations. In general, the form of a material object is simply the configuration of its material parts: “We call the form strictly what comes from the composition of the parts.” The form of a statue, for example, is its shape, which is nothing more than the arrangement of its matter—the curve of the nose, the size of the eyes, and so on. Forms are therefore supervenient on matter and lack independent ontological standing. This does not deny the existence of forms but provides a specific explanation of form inherence: a subject possesses a form when its matter is configured in a particular way. For instance, the shape of a statue is inherent in it simply by virtue of how its bronze is arranged. Material things, therefore, are fundamentally identical to their material constituents, with one exception: human beings, whose forms are their immaterial and immortal souls. Strictly speaking, human souls, capable of existing separately from the body, are not truly forms, although they function as substantial forms when united with the body.

Material composites of form and matter, excluding humans, are integral wholes composed of discrete material parts arranged in a specific configuration. Abelard acknowledged various types of integral wholes: collections, regardless of member selection; structured composites, both naturally unified (Socrates and his limbs) and artificially unified (house walls, floor, and roof); continuous quantities of homogeneous material “substances,” like water or gold; geometrical objects defined by part positions; and temporal wholes (days and their constituent hours). Most of these wholes are ontologically reducible to their material parts. The independent ontological status of structured composites depends on the status of their organizing forms.

Abelard’s theory of substantial integral wholes is not purely mereological in the modern sense because he recognized privileged divisions. Just as a genus is properly divided into its proximate species, the division of a whole must be into its principal parts. Intuitively, some wholes possess a natural division that takes precedence over others; a sentence, for instance, is divided into words, syllables, and letters in that specific order. According to Abelard, the principal parts of a whole are those whose combination directly produces the complete whole. His intention seems to be that the nature of the composition defining the integral whole also defines its principal parts. A house is composed of floor, walls, and roof assembled correctly. It remains an open question whether each principal part (like a wall) necessitates the existence of all its subparts (every brick). The principal parts of a collection are simply its members, regardless of the subparts of any member. The principal parts of an aggregation are its members located in proximity.

Individuals possess natures, and by virtue of these natures, they belong to specific natural kinds. However, an individual’s nature is not genuinely shared or common with other individuals; Abelard’s refutation of realism demonstrated the impossibility of such shared essences. Instead, Abelard defined a natural kind as a well-defined collection of things sharing features that broadly define their identity. Why a thing possesses certain features is explained by its origin—the natural processes of its creation result in its specific features, making it the kind of thing it is. Similar processes yield similar outcomes. On this interpretation, natural kinds lack special ontological status; they are simply discrete integral wholes categorized by similarity, reflecting the world’s division into similarity-classes of objects. Furthermore, these real relations of similarity are not entities separate from the similar things themselves. The division into natural kinds is, presumably, a “shallow fact” about the world: things could have been different had God ordained them so; fire might be cold, heavy objects might fall upwards, and frogs might reason. If causal powers were different, natural kinds might also be different or less sharply defined. As things are, natural kinds reflect the world’s inherent structure, but these structures are ultimately chosen by God.

3. Logic: Abelard’s Revolution in Logical Thought

Peter Abelard is recognized as the most significant logician from antiquity until the rise of modern logic. He developed a purely truth-functional propositional logic, anticipating Frege’s distinction between force and content, and formulated a comprehensive theory of entailment as it functions in argumentation, a precursor to modern theories of logical consequence. While his system has limitations in its treatment of topical inference, Abelard’s achievements in logic remain profound.

Abelard observed that the same propositional content can be expressed with varying force depending on context. The content that Socrates is in the house is expressed as an assertion in “Socrates is in the house,” as a question in “Is Socrates in the house?”, as a wish in “If only Socrates were in the house!”, and so on. This insight allowed Abelard to distinguish between the assertive force of a sentence and its propositional content. This distinction is crucial for understanding that component sentences within a conditional statement are not asserted, even though they carry the same content they would if asserted independently. For example, in “If Socrates is in the kitchen, then Socrates is in the house,” neither “Socrates is in the kitchen” nor “Socrates is in the house” is asserted, despite using the same words that could be used to make assertions outside the conditional context. Similarly, this distinction enabled Abelard to define negation and other propositional connectives purely truth-functionally in terms of content. Negation, for instance, is treated as follows: not-p is false/true if and only if p is true/false.

For Abelard, the concept of inferentia, best translated as “entailment,” is central to the theory of argument. Entailment requires a connection between propositions that is both necessary and relevant. The conclusion—more precisely, the sense of the final statement—must be necessitated by the sense of the preceding statement(s), making it impossible for the conclusion to be false if the premises are true. Abelard often spoke of the conclusion’s sense being “contained” within the sense of the premises, mirroring our modern notion of a conclusion being logically contained in the premises. An entailment is complete (perfecta) when it holds due to the logical form (complexio) of the propositions involved. By this, Abelard explained, he meant that the entailment remains valid under any uniform substitution of its terms—the criterion now associated with Bolzano. The traditional figures and moods of categorical syllogism from Aristotle and the theory of hypothetical syllogism from Boethius are all instances of complete entailments, or what we would now call valid inferences.

However, necessity and relevance between premises and conclusions can also arise in ways that are not formally valid (i.e., not complete entailments). The necessary connection and the link between senses might stem from non-formal metaphysical truths that hold in all possible worlds. For example, “human beings are a kind of animal,” so the inference “If Socrates is a human being, Socrates is an animal” is necessarily true, and the sense of the antecedent necessitates the sense of the consequent. Yet, this is not formally valid under uniform substitution. Abelard considered such incomplete entailments to fall under the theory of topics, representing forms of so-called topical inference. The example above is validated by the topic “from the species,” a set of metaphysical relations, one of which is expressible as the rule “Whatever the species is predicated of, so too is the genus,” which grounds the inferential force of the entailment. Against Boethius, Abelard argued that topical rules were only necessary for incomplete entailments and were not required to validate the classical moods of categorical and hypothetical syllogisms.

Abelard devoted significant effort to exploring the complexities of topical inference, particularly mapping the relationships between conditional sentences, arguments, and what he termed “argumentation” (roughly, what follows from conceded premises). One surprising outcome of his investigation was his rejection of a direct correlate to the Deduction Theorem. He maintained that a valid argument does not necessarily correspond to an acceptable conditional sentence, and vice versa, because the criteria for arguments and conditionals differ.

Ultimately, Abelard’s principles of topical inference proved problematic. Their shortcomings became evident concerning the topic “from opposites,” where Abelard’s principles led to inconsistencies, as noted by Alberic of Paris. This triggered a crisis in 12th-century inference theory, as Abelard’s attempts to resolve the difficulty were unsuccessful. These debates seem to have occurred in the late 1130s, as Abelard became entangled with Bernard of Clairvaux, diverting his attention from these logical intricacies.

4. Philosophy of Language: Semantics and Meaning for Abelard

A substantial portion of Peter Abelard’s philosophy of language is dedicated to analyzing the logical function of expressions and expression classes: identifying quantifiers, negation indicators, and so on, to enable the application of his logical system. He relied on the traditional Aristotelian division of linguistic categories into name, verb, and their combination in the sentence.

Abelard defined names as conventionally significant simple words, typically without tense. This broad definition included proper and common names, adjectives and adverbs, pronouns (personal, possessive, reflexive, relative), conventional interjections, and arguably conjunctions and prepositions (despite lacking definite signification), along with participles and gerundives (which have tense). He often treated compound names like ‘street-sweeper’ reductively. Despite this extensive list, it did not fully encompass all referring expressions. In practice, much of Abelard’s discussion of name semantics centered on common names, which were central to the problem of universals and posed unique semantic challenges.

When Abelard asserted that universality is solely a linguistic phenomenon, that universals are “nothing more than words,” he addressed the objection that if common names do not name common entities, they become meaningless, rendering his view no better than that of his teacher Roscelin (who considered universals mere vocal sounds). In response, Abelard clearly distinguished between two semantic properties of names: reference (nominatio), what a term applies to; and sense (significatio), what hearing a term evokes in the mind, or more precisely, the informational content (doctrina) of the concept the word is intended to generate—a causal notion.

Names, both proper and common, refer to things individually or severally. A name is linked to its referent as if someone devised the name to label a specific thing or kind of thing—a process called “imposition” (modeled on Adam naming animals in Genesis 2:19), akin to baptism. This rational reconstruction of reference does not require the “impositor” to have more than a vague intention to designate a thing or kind, regardless of its precise nature:

The inventor [of names] intended to impose them according to some natures or distinctive properties of things, even if he himself did not know how to think correctly upon the nature or distinctive property of a thing.

A name “has a definition in the nature of its imposition, even if we do not know what it is.” In modern terms, Abelard advocated a theory of direct reference, where a term’s extension is not determined by its sense. We can be completely ignorant of the proper conceptual content associated with a successfully imposed term.

Proper names—names of primary substances—signify a concrete individual (hoc aliquid), distinguishing its bearer personally from all others. Therefore, proper names are semantically singular referring expressions, closely related to indexicals, demonstratives, and singular descriptions (or descriptive terms). Common names, in contrast, are semantically linked to expressions with what Abelard termed “plural signification.” On one hand, common names resemble plural nouns; the common name ‘man’ is grammatically singular but functions like the plural term ‘men’—each refers to every man, though plural terms signify individuals as part of a collection, while common names refer distributively to each individual. On the other hand, common names are similar to terms like ‘trio’ or ‘pair’ in that they designate a specific plurality of individuals, but only in a context of use, as their extension is variable.

Thus, a common name distributively refers to concrete individuals, but not qua individuals. Instead, it severally designates individuals possessing a given nature: ‘human being’ refers to Socrates and Plato because each is human. This is not a shared feature in any ontological sense. Socrates is simply what he is, human, and Plato is also human. Abelard clearly stated his deflationary stance in his Logica ‘ingredientibus’:

Now it seems we should stay away from accepting the agreement among things according to what is not any thing—it’s as though we were to unite in nothing things that now exist!—namely, when we say that this [human] and that one agree in the human status, that is to say: in that they are human. But we mean precisely that they are human and don’t differ in this regard—let me repeat: [they don’t differ] in that they are human, although we’re not appealing to any thing [in this explanation].

Socrates and Plato are real; their agreement is also real, but it is not explained by appealing to any thing—their agreement is simply their each being human. Metaphysically, they have the same standing as human beings, without any metaphysically shared component or any component at all. This is the “common reason” for imposing a common name.

While signification is secondary to reference, names do possess signification. Abelard held that a term’s signification is the informational content of the concept associated with the term upon hearing it, under normal circumstances. Because names are only conventionally significant, the concept associated with a name depends partly on the psychological conditioning of language users. Abelard could thus treat signification as both a causal and a normative concept: the word ‘rabbit’ should cause native English speakers to form the concept of a rabbit upon hearing it. Abelard emphasized that signification is about the informational content within the concept—mere psychological associations, even mental images linked to a concept, are not part of a word’s meaning. Ideally, the concept corresponds to a real definition that captures the essence of the thing, like ‘rational mortal animal’ being considered the real definition of ‘human being’, irrespective of other associated features (even necessary ones like risibility) or contingent images (any mental image of a human will be of someone with specific features). Achieving conceptual clarity is a demanding task, requiring understanding how understanding itself operates. However, the example clarifies a crucial point: the significations of some names, like natural-kind terms, are abstractions, including only certain features of the referents. They do not positively exclude other features and can be further specified: ‘rational mortal animal’ as the content of ‘human being’ signifies all humans, regardless of further traits—tall or short, male or female, etc.

What applies to name semantics largely applies to verbs. The distinguishing feature of verbs, more than tense or grammatical person, is their connective force (vis copulativa). This is a fundamental, irreducible characteristic of verbs, activated only when combined with names syntactically, reminiscent of Frege’s notion of conceptual “unsaturatedness.” Sentences are constructed from names and verbs so that the whole sentence’s meaning is a function of its parts’ meanings. Abelardian semantics is fundamentally compositional. The specifics of composition are complex. Abelard worked directly with Latin, a natural language that, despite its artificiality, was still a living tongue. He analyzed numerous linguistic phenomena that a more formal framework would simply exclude.

For instance, Abelard noted that most verbs can function as predicates in two ways: as a finite verbal form or as a nominal form combined with an auxiliary copula. We can say either ‘Socrates runs’ or ‘Socrates is running’; similarly, ‘Socrates hits Plato’ and ‘Socrates is hitting Plato.’ Abelard argued that the pure verbal form of predication is fundamental, explaining and clarifying the extended version. The latter is necessary mainly when simple verbal forms are lacking (the substantive verb ‘is’ requires special treatment). Thus, for Abelard, basic predication analysis recognizes the joining of two fundamentally different linguistic categories: the name n and the simple verbal function V( ), combined into the well-formed sentence V(n).

Abelard argued that sentences (propositiones) must signify more than just the understandings of their constituent name and verb. First, a sentence like ‘Socrates runs’ is about Socrates and running, not about anyone’s understandings of them. We discuss the world, not merely someone’s understanding of it. Second, sentences like ‘If something is human, it is an animal’ are false if interpreted as being about understandings, because someone could have the concept human without having the concept animal, making the antecedent true without the consequent. Third, understandings are fleeting particulars, mental tokenings of concepts. But at least some consequential sentences are necessary, and necessity cannot be based on transient things like understandings. Sentences must therefore signify something beyond understandings, something capable of what understandings cannot achieve. Abelard called this sentence-signified entity the dictum (plural dicta)—what the sentence says.

To modern philosophical ears, Abelard’s dicta might sound like propositions, abstract, timeless bearers of truth and falsity. However, Abelard explicitly rejected such entities. He repeatedly and emphatically stated that dicta, though distinct from and more than the sentences expressing them, have no ontological existence whatsoever. In a single paragraph, he declared them “no real things at all” and twice called them “absolutely nothing.” They ground sentences, but they are not real entities. While a sentence says something, there is no thing that it says. The semantic function of sentences is to say something, which is not naming or denoting a thing. It is proposing how things are, without a realist interpretation. Similarly, the truth of true sentences is not a property inherent in a timeless entity but simply the assertion of what the sentence says—Abelard adopted a deflationary account of truth. A sentence is true if things are as it says, and things make sentences true or false by virtue of their nature (and what the sentences say), requiring nothing further. The sentence ‘Socrates runs’ is true because Socrates runs, which is all that can and needs to be said.

5. Philosophy of Mind: Intentionality and Understanding for Peter Abelard

Aristotelian philosophy of mind offered two explanations of intentionality: the conformality theory, which posits that we think of an object by having its form in the mind, and the resemblance theory, which suggests mental images in the mind naturally resemble the object. Abelard rejected both, proposing an adverbial theory of thought, arguing that neither mental images nor mental contents need ontological independence from the mind. He offered a contextual explication of intentionality based on a linguistic account of mental representation, adopting a principle of compositionality for understandings.

The first Aristotelian analysis, conformality theory, holds that understanding is the mind’s acquisition of the understood object’s form, without its matter. To understand something—say, a cat—is for the form of cat to be in the mind or intellective soul. Form inherence in matter makes matter a thing of a certain kind. Thus, the inherence of the form cat in matter creates an actual cat. Conversely, the (immaterial) inherence of the form cat in the mind transforms the mind into an understanding of a cat: the mind becomes (formally) identical with its object. Since the “aboutness” of understanding is analyzed as the shared or identical form in understanding and the understood thing, this is called the conformality theory. It captures the intuition that understanding somehow inherits or includes properties of what is understood by reducing intentionality to the objective identity of form in mind and world.

The second Aristotelian analysis, resemblance theory, posits that understanding is the mind’s possession of a concept that is a natural likeness of, or naturally similar to, what it is a concept of. To understand a cat, for example, is to have an occurrent concept in mind that is a natural likeness of a cat. The “naturalness” of the likeness ensures that the resemblance between understanding and object is objective and that all people have access to the same set of concepts (conformality theory achieves this through objective forms and a universal process of form assimilation). This is the resemblance theory: mental acts are classified by their degree and kind of resemblance to the things understood.

Resemblance theory faces challenges in defining “resemblance” or “likeness.” A concept is immaterial and radically different from material objects. Furthermore, there seems to be no formal characteristic of a mental act that non-trivially resembles anything. To address these issues, medieval philosophers, like later British Empiricists, appealed to pictorial resemblance. A portrait of Socrates is about Socrates because it visually resembles him. Similarly, mental images are about things. These images, whether concepts themselves or within concepts, explain how concepts are “about” objects. Understanding a cat means having or containing a mental image of a cat. Mental “aboutness” is explained by pictorial aboutness, reduced to a real relation of resemblance.

Despite Aristotelian origins, conformality and resemblance theories are not equivalent. Mind transformation through form inherence differs from concept possession. Natural likeness need not be formal identity; formal identity need not imply genuine resemblance due to different subjects embodying the form.

The standard way to reconcile these theories is to equate concept possession with the mind’s ability to transform through form inherence, construing formal identity as natural likeness. Having a form in mind identical to the object’s form is having a mental image of that object.

Abelard argued against conformality using the example of a tower, a material object with length, depth, and height—its form, analogous to a statue’s shape. Aristotelian metaphysics holds that form inherence in a subject makes the subject characterized by that form. Forms of the tower (length, width, massiveness) are physical properties. If these forms inhere in the mind, they should make the mind tall, wide, and massive—an absurd conclusion: the mind “cannot extend itself in length or width.” Yet, conformality theory asserts the mind has the identical form of the external object, even though length is inherently physical. Thus, Abelard concluded, conformality is incoherent.

Abelard’s main objection to resemblance theory was that mental images qua images, like any sign, are inert and require interpretation. A sign is just an object, capable of significative roles but not inherently so. This distinction applies to non-mental signs as well: a statue can be seen as bronze or as a likeness. Mental images are similarly inert. Sign function requires more than mere presence. Resemblance theory fails to recognize the need to interpret the mental image as an image, mistakenly equating understanding with mere mental image presence. Abelard concluded mental images play only an instrumental role in thought, calling them “intermediary signs of things” (intersigna rerum). Intentionality arises instead from attentio, the act of attention directed at the mental image. Proof lies in the fact that we can “vary understanding” by attending to different image features. The same image—say, a fig tree—can be used to think about that tree, trees generally, plant life, or a past love associated with it. No intrinsic image feature dictates its referent. If there were, Abelard noted, we could determine a sign’s referent by inspection, which is impossible. Mental images cannot explain intentionality because their role is merely instrumental. We think with them, but they do not explain intentionality.

Abelard concluded that intentionality is a primitive, irreducible feature of the mind—our acts of attending to things. Different acts of attention are intrinsically different, about what they are about by virtue of their nature as specific acts of attention. He thus adopted an adverbial theory of thought.

Given primitive intentionality, Abelard took a contextual approach to mental content, embedding acts of attention in a structure whose articulation defines constituent elements. This structure is linguistic—a logic of mental acts. Just as words express thoughts, language logic can provide a theory of understanding. Abelard presented a linguistic account of mental representation or intentionality, embracing compositionality: an understanding’s object is a function of its constituent understandings’ objects. The unity of a complex understanding depends on its logical simplicity, marked by “a single dominant conjunction” (the widest-scope logical operator). Complex understanding is a complex of distinct understandings, aggregated in thought, with (logical) structure from the “dominant conjunction” governing constituent understandings. Abelard’s acts of attention thus display the logical structure of understanding, providing semantics for written or spoken language. Much of Abelard’s logic and dialectic writings detail this scheme for explicating mental content.

6. Ethics: Intentionalism and Moral Worth According to Abelard

Abelard’s ethics are rooted in a radical intentionalism, arguing that an agent’s intention alone determines the moral worth of an action. He rejected the moral relevance of consequences, highlighting what contemporary philosophers call moral luck. Consider two men intending and having the means to build shelters for the poor, but one is robbed before acting, while the other succeeds. Abelard argued that to morally differentiate them is to suggest “the richer men were the better they could become … this is the height of insanity!” Deed-centered morality, he argued, loses sight of moral potential. It also fails to account for epistemic status, neglecting the moral excusability of ignorance. Abelard illustrated this with fraternal twins, brother and sister, separated at birth, unaware of each other’s existence. Meeting as adults, they fall in love, marry, and have intercourse. Technically incest, Abelard found no moral fault in either, given their ignorance.

Abelard concluded that deeds are morally indifferent in themselves. Moral evaluation should focus on the agent’s intentions. One might object that deed performance or non-performance affects feelings, which in turn affect intentions, granting deeds indirect moral relevance. Abelard denied this:

For example, if someone forces a monk to lie bound in chains between two women, and by the softness of the bed and the touch of the women beside him he is brought to pleasure (but not to consent), who may presume to call this pleasure, which nature makes necessary, a fault?

Pleasure, in certain situations (sex, delicious food), is inevitable. If marital sexual pleasure is not sinful, then pleasure itself is not sinful, inside or outside marriage. If it is sinful, marriage cannot sanctify it. If acts should be pleasureless, Abelard declared them impossible, and God unreasonably permits them only in an impossible way.

Abelard argued that intentionalism is essential to explain why coercion and ignorance (more precisely, negligence) excuse agents. He controversially argued that Christ’s crucifiers were not evil in crucifying Jesus. Their ignorance of Christ’s divinity did not make them evil, nor did acting on their mistaken beliefs. Non-negligent ignorance absolves blame. In fact, Abelard claimed they would have sinned had they believed crucifying Christ necessary and not done it. Regardless of facts, acting against conscience is blameworthy.

Two objections arise against Abelard’s intentionalism. First, how is voluntary evil possible? Second, since intentions are private, is ethical judgment impossible?

To the first, Abelard offered a twofold answer. We often want the deed but not the punishment—wanting sex but not adultery, preferring an unmarried partner. We also “want what we by no means want to want”—bodies react with pleasure and desire independently of will. Acting on such desires is “of” will, but not voluntary. Desire is not evil; acting on it is, even with conflicting desires.

To the second, Abelard conceded that humans cannot know intentions—only God can, allowing for Final Judgment. However, ethical judgment is not impossible. Only God has the right to judge morally. Human justice, however, is primarily exemplary and deterrent. Just punishment may even be inflicted on someone believed to lack evil intent. He cited a woman accidentally smothering her baby while trying to keep it warm. Punishment serves as an example to other poor mothers to be more careful. Similarly, a judge with strong (but legally inadmissible) evidence of perjury must rule based on perjured testimony, condemning an innocent accused. Human justice can properly disregard intention. Divine justice remains, making ethical notions relevant, even for human justice, as they guide which intentions to promote or discourage through exemplary punishment.

Therefore, the only truly certifiable sin is acting against conscience, absent negligence. But if deeds and consequences are irrelevant, how are permissible/obligatory acts determined? Without reliable conscience guidance, Abelard’s position risks subjective moral chaos.

Abelard resolved this by grounding obedience to God’s will—the hallmark of moral behavior and natural law—in intention conforming to a purely formal criterion: the Golden Rule (“Do to others as you would be done to”). Reason alone discovers this rule, without revelation or religious belief, ensuring right intention. However, why should one care about the Golden Rule? Why be moral?

Abelard answered that happiness—a universal human desire—is linked to virtue, to habitual moral conduct. His Collationes argues that reason shows naturalistic ethics insufficient, and happiness is bound to Christian belief, including God and afterlife. The afterlife is a morally superior condition to strive for, even beyond virtuous earthly life. Recognizing this constitutes wanting God’s will, living by the Golden Rule, and securing (with divine grace) postmortem happiness.

The Philosopher first debated the Jew, espousing “strict observance” morality—obedience to Mosaic Law. The Jew offered a Slave’s Wager (an early version of Pascal’s Wager). A Slave, told by a stranger about his irritable Master’s instructions, reasons: if instructions exist, obedience brings reward, disobedience punishment; if not, obedience brings no punishment, disobedience minor punishment. This mirrors Pascal’s Wager payoff matrix. This is the Jew’s position: God demands Mosaic Law obedience—the given instructions. The Philosopher argued for alternative actions and that ethics is about intentions, not legalistic action.

The Philosopher then debated the Christian, initially claiming virtue entails happiness, negating the need for afterlife, as a virtuous person remains in the same state dead or alive. The Christian countered that afterlife is superior, adding to virtuous life the absence of circumstantial impediments. In afterlife, freed from bodily constraints, one is not bound by physical necessities. Agents can achieve pure happiness through virtue, unhindered by external factors. The Philosopher conceded the afterlife is a clear improvement, joining the Christian to define virtues and the Supreme Good. Virtue is its own reward, and afterlife allows maximizing virtuous reward, unimpeded.

7. Theology: Reason and Faith in Abelard’s Thought

Abelard believed reason had a limited but significant role in matters of faith. This stance brought him into conflict with “anti-dialecticians” like Bernard of Clairvaux, who opposed any role for reason, and with “pseudo-dialecticians” like Roscelin, his former teacher, who overemphasized reason.

Bernard and other anti-dialecticians seemed to believe that religious propositions, to the extent comprehensible, had plain meanings. Beyond this, nothing was graspable, rendering reason unhelpful. They were semantic realists about plain religious sentence meaning. They criticized Abelard for obscuring plain meanings through reasoning, which they deemed irrelevant to grasping plain meaning (immediate, without reason) or achieving deeper understanding (only plain meaning being accessible).

Abelard rejected the semantic realism underpinning the anti-dialectical position. Rather than direct refutation, he undermined it. From scriptural and dogmatic commentaries to speculative theology, Abelard aimed to demonstrate the comprehensibility of religious claims, particularly how dialectical methods clarified faith propositions. He also rejected the notion of plain meaning. In Sic et non‘s prologue, Abelard described his method: posing a question (e.g., priestly celibacy) and then arranging scriptural and patristic citations that seemingly directly answer it, into positive and negative responses. He then offered methods for resolving apparent contradictions: checking for word ambiguity, examining context, making relevant distinctions, ensuring the author’s voice is distinguished from reported positions, etc. Each authority cited seemed to speak clearly and unambiguously for or against a given proposition. If plain meaning existed anywhere, it seemed to be in authoritative pronouncements on opposing sides of controversies. Abelard’s prologue advice suggested that sentences appearing to exemplify plain meaning must be carefully scrutinized to uncover their actual meaning. This implies they lack plain meaning altogether; reason is needed to discern their meaning. Thus, anti-dialecticians lacked a valid argument.

Abelard identified a more significant threat to reason in religion (Theologia christiana 3.20):

Those who claim to be dialecticians are usually led more easily to [heresy] the more they hold themselves to be well-equipped with reasons, and, to that extent more secure, they presume to attack or defend any position the more freely. Their arrogance is so great that they think there isn’t anything that can’t be understood and explained by their petty little lines of reasoning. Holding all authorities in contempt, they glory in believing only themselves—for those who accept only what their reason persuades them of, surely answer to themselves alone, as if they had eyes that were unacquainted with darkness.

These “pseudo-dialecticians” considered reason the ultimate arbiter of all claims, including faith claims. Abelard accused them of believing: (a) everything is explicable by human reason; (b) we should only accept what reason persuades us of; (c) appeals to authority lack rational persuasive force. True dialecticians, he argued, reject (a)–(c), recognizing reason’s limits and that some vital truths may lie beyond reason but not beyond belief. Which faith claims to accept depends on both source reliability (authorities) and rational consistency where investigable.

Abelard’s arguments against (a)–(c) were sophisticated. To show reason’s fruitful application to faith articles, he offered his Trinity investigation as a case study. His theology work largely involved dialectical examination of the Trinity. He developed an original identity theory to address Trinity issues, with broader metaphysical applicability. His inquiries concluded that Trinity belief is rationally justifiable; reason, as far as it can reach, finds the doctrine sensible, especially with proper dialectical tools.

Traditional identity theory, from Boethius, considered generic, specific, and numerical sameness or difference. Abelard accepted this but found it insufficiently nuanced for the Trinity. His Theologia christiana theory added four identity modes: (1) essential sameness/difference; (2) numerical sameness/difference (closely tied to essential sameness, offering finer distinctions); (3) sameness/difference in definition; (4) sameness/difference in property (in proprietate). Essential and numerical sameness refined identity conditions for worldly entities. Sameness in definition provided identity conditions for entity features. Sameness in property allowed different identity conditions for a single entity with distinct features.

Abelard defined essential sameness as two things being numerically the same concrete thing (essentia), and essentially different otherwise. The Morning Star and Evening Star are essentially the same, both being Venus. Formal elements constituting a concrete thing are essentially the same as each other and the concrete thing they constitute: Socrates is his essence (Socrates is what it is to be Socrates). This does not hold for parts. Abelard maintained a part is essentially different from the integral whole, being contained in the whole and thus quantitatively less.

Numerical difference does not perfectly align with essential difference. Numerical non-sameness arises in two cases. First, objects are not numerically the same when one contains a part the other lacks, in which case they are also essentially different. Second, objects are numerically different when neither contains a part of the other. Numerical difference implies numerical non-sameness, but not vice versa: a part is not numerically the same as its whole, but not numerically different either. Thus, essential difference occurs when objects share only a part (numerically non-same) or share no parts (numerically different and non-same). As things can be neither numerically same nor numerically different, the question “How many things are there?” is ill-formed without further specification—a point Abelard used in Trinity discussions.

Essential and numerical sameness/difference apply to worldly entities, being extensional identity forms. Sameness/difference in definition is analogous to modern property identity theories. Abelard held things are definitionally same when being one necessitates being the other, and vice versa; otherwise, they differ definitionally.

Finally, things are property-same when they specify mutually characterizing features. A marble cube exemplifies whiteness and hardness. Whiteness and hardness are essentially the same, being the same marble cube. Yet, whiteness and hardness definitionally differ. However, whiteness is characterized by hardness (the white thing is hard), and hardness by whiteness (the hard thing is white). Properties are “mixed”—definitionally different, yet each applies to the same concrete thing (marble cube) both as itself and as characterized by the other.

The interesting case is when properties remain “completely unmixed,” leading to property-different items. Consider a form-matter composite and its matter. Matter and composite are essentially the same, both being the whole material composite. Yet, they are not identical; matter is not the composite, nor vice versa. The composite comes from matter, but matter does not come from itself. The composite is not matter because “nothing is in any way a constitutive part of or naturally prior to itself.” Matter is prior to composite, having priority concerning it, while composite is posterior to matter, having posteriority. Despite essential sameness, matter lacks posteriority, and composite lacks priority. Thus, matter and composite are property-different; priority and posteriority are unmixed.

Abelard applied this identity theory to illuminate the Trinity. The three Persons are essentially the same, all being the same concrete entity (God). They differ definitionally, as being the Father is not the same as being the Son or Holy Spirit. The three Persons are numerically different, or they would not be three, but not numerically different from God; otherwise, there would be three gods. Each Person has unique properties—unbegotten for the Father, begotten for the Son, proceeding for the Holy Spirit—and distinctive properties like power for the Father, wisdom for the Son, and goodness for the Holy Spirit. Unique properties are unmixed (Persons differ in them, and they do not apply to God). Distinctive properties are mixed (God is characterized by each—powerful, wise, and good). Human reason, Abelard argued, cannot go further, but it validates the analysis (strictly an analogy) as far as possible.

Bibliography

Primary Texts in Latin

Carmen ad Astralabium. Edited by J. M. A. Rubingh-Bosscher in Peter Abelard: Carmen ad Astralabium, a Critical Edition. Groningen: phil. diss. Rijksuniversiteit 1987.
Collationes a.k.a. Dialogus inter Philosophum, Iudaeum, et Christianum. Edited by Giovanni Orlandi, with introduction, translation, and notes by John Marenbon, in Peter Abelard: Collationes, Oxford University Press 2001.
Commentaria in Epistolam Pauli ad Romanos. Edited by Eligius M. Buytaert in Petri Abaelardi opera theologica. Corpus christianorum (continuatio mediaevalis) Vol. 11. Brepols: Turnholt 1969, 389–340.
Dialectica. Edited by L. M. De Rijk in Petrus Abaelardus: Dialectica, Assen: Van Gorcum 1970 (second edition).
Epistolae: Ep. 1 edited by Monfrin (see the entry below for the Historia calamitatum); Epp. 2–5 edited by J. T. Muckle, Mediaeval Studies 15 (1953) 68–94; Epp. 6–7, edited by J. T. Muckle, Mediaeval Studies 17 (1955) 241–281; Ep. 8, edited by T. P. McLaughlin, Mediaeval Studies 18 (1956) 242–297; Epp. 9–14 edited by E. R. Smits in Peter Abelard: Letters IX–XIV, Groningen: Rijksuniversiteit 1983; Ep. 15 edited by Josef Reiners, BGPTM 8 (1910) 63–80; Ep. 16, edited by Victor Cousin and Charles Jourdain, Petri Abaelardi opera Vol. 1 (Paris 1849) 703–707, corrected against Van Den Eynde, Antonianum 38 (1963) 219; Ep. 17, edited by Charles Burnett, Mittellateinisch Jahrbuch 21 (1986), 152–155; Apologia contra Bernardum (Ne iuxta Boethianum), edited by Eligius M. Buytaert in CCCM 12 359–368; Epistola contra Bernardum edited by Raymond Klibansky, Medieval and Renaissance Studies 5 (1961), 1–27; Confessio fidei “Uniuersis” edited by Charles Burnett, Mediaeval Studies 48 (1986), 182–189.
Ethica seu Scito teipsum. Edited by R. M. Ilgner in Petri Abaelardi opera theologica. Corpus christianorum (continuatio mediaevalis) Vol. 190. Brepols: Turnholt 2001.
Expositio orationis dominicae. Edited by Charles Burnett, “Expositio orationis dominicae ‘Multorum legimus orationes’” in Révue Benedictine 95 (1985) 60–72.
Expositio symboli Apostolorum. Edited by Victor Cousin and Charles Jourdain, Petri Abaelardi opera Vol. 1 (Paris 1849) 603–615. [Available online thanks to the Bibliothèque nationale de France].
Expositio fidei in symbolum Athanasii. Edited by Victor Cousin and Charles Jourdain, Petri Abaelardi opera Vol. 1 (Paris 1849) 615–617.
Hexaëmeron. Edited by Mary F. Romig with the assistance of David Luscombe, in Corpus christianorum continuatio mediaevalis Vol.15. Brepols: Turnhout 2004.
Historia calamitatum. Edited by Jacques Monfrin in Abélard, Historia calamitatum: texte et commentaires, J. Vrin: Paris 1974 (fourth edition), 62–109.
Hymnarius Paraclitensis. Edited by Chrysogonus Waddell in Hymn Collections from the Paraclete Vol. 2. Trappist Monastery, Ky.: Gethsemani Abbey (Cistercian Liturgy series) 1987.
Introductiones parvulorum. Edited by Mario Dal Pra in Pietro Abelardo: Scritti di logica, Firenze 1969 (second edition).
Logica ‘ingredientibus’ (LI):
- LI 1: Commentary on Porphyry’s Isagoge. Edited by Bernhard Geyer in Beiträge zur Geschichte der Philosophie und Theologie des Mittelalters 21 (1). Aschendorff: Munster 1919.
- LI 2: Commentary on Aristotle’s Categories. Edited by Bernhard Geyer in Beiträge zur Geschichte der Philosophie und Theologie des Mittelalters 21 (2). Aschendorff: Munster 1921.
- LI 3: Commentary on Aristotle’s De interpretatione. Edited by Klaus Jacobi and Christian Strub, Corpus christianorum continuatio mediaevalis Vol.206. Brepols: Turnhout 2010.
- LI 7: Commentary on Boethius’s De topicis differentiis. Edited by Mario Dal Pra in Pietro Abelardo: Scritti di logica, Firenze 1969 (second edition).
Logica ‘nostrorum petitioni sociorum’. Commentary on Porphyry’s Isagoge. Edited by Bernhard Geyer in Beiträge zur Geschichte der Philosophie und Theologie des Mittelalters 21 (4). Aschendorff: Munster 1933.
Planctus. Planctus 1, 4, 6: edited by Peter Dronke, Poetic Individality in the Middle Ages (London 1986). Planctus 2, 5: edited by Giuseppe Vecchi, Pietro Abelardo, I “Planctus” (Modena 1951). Planctus 3: edited by Wolfram von den Steinen, Mittellateinisches Jahrbuch 4 (1967), 122–144. There are several modern recordings.
Problemata Heloïssae cum Petri Abaelardi solutionibus. Edited by Victor Cousin and Charles Jourdain, Petri Abaelardi opera Vol. 1 (Paris 1849): 237–294.
Sententiae secundum Magistrum Petrum. Edited by Lorenzo Minio-Paluello in Twelfth-Century Logic: Texts and Studies Vol. 2 (Abaelardiana inedita), Roma 1958.
Sermones. Edited by Paola De Santis in I sermoni di Abelardo per le monache del Paracleto, Leuven University Press 2002. (Mediaevalia Lovaniensa ser. 1, studia 31.)
Sic et non. Edited by Blanche Boyer and Richard McKeon in Peter Abailard: Sic et Non. A Critical Edition. University of Chicago Press 1977.
Soliloquium. Edited by Charles Burnett in “Peter Abelard’s ‘Soliloquium’: A Critical Edition” in Studi Medievali 25 (1984), 857–894.
Theologia ‘summi boni’. Edited by Eligius M. Buytaert and Constant Mews in Petri Abaelardi opera theologica. Corpus christianorum (continuatio mediaevalis) Vol. 13. Brepols: Turnhout 1987.
Theologia christiana. Edited by Eligius M. Buytaert in Petri Abaelardi opera theologica. Corpus christianorum (continuatio mediaevalis) Vol. 12. Brepols: Turnhout 1969.
Theologia ‘scholarium’. Edited by Eligius M. Buytaert and Constant Mews in Petri Abaelardi opera theologica. Corpus christianorum (continuatio mediaevalis) Vol. 13. Brepols: Turnhout 1987.
Tractatus de intellectibus. Edited by Patrick Morin in Abélard: Des intellections. Paris: J. Vrin 1994.

Primary Texts in English Translation

Fairweather, E. R., 1995, A Scholastic Miscellany, Westminster: John Knox Press. (Excerpt from Abelard’s commentary on Romans.)
King, Peter, 1982, Peter Abailard and the Problem of Universals in the Twelfth Century, Ph.D. Dissertation, Philosophy Department, Princeton University. (Volumes 2 contains a complete translation of Abelard’s Tractatus de intellectibus.)
Luscombe, David, 1971, Ethics, Oxford: Oxford University Press. (Complete translation of Abelard’s Ethica.)
Marenbon, John and Giovanni Orlandi (eds. and trans.), 2001, Peter Abelard: Collationes, Oxford: Clarendon. (Complete translation of Abelard’s Conversations.)
McCallum, James Ramsay, 1948, Abelard’s Christian Theology, Oxford: Blackwell. (Includes substantial selections from Abelard’s Theologia christiana.)
Minnis, A. and Scott, A. B. (eds.), 1988, Medieval Literary Theory and Criticism 1100–1375, Oxford: Oxford University Press. (Includes Abelard’s preface to the Sic et non.)
Payer, Pierre, 1979, Peter Abelard: A Dialogue of a Philosopher with a Jew and a Christian, Toronto: The Pontifical Institute of Mediaeval Studies Publications.
Radice, Elizabeth, 1974, The Letters of Abelard and Heloise, New York: Penguin Books.
Spade, Paul Vincent, 1994, Five Texts on the Mediaeval Problem of Universals, Indianapolis: Hackett Publishing Company. (Abelard’s discussion of the problem of universals from his Logica ‘ingredientibus’.)
Spade, Paul Vincent, 1995, Peter Abelard: Ethical Writings, Indianapolis: Hackett Publishing Company. (Complete translations of Abelard ‘s Ethics and Conversations.)
Tweedale, Martin and Bosley, Richard, 1997, Issues in Medieval Philosophy, Peterborough: Broadview Press. (Includes selections from Abelard on foreknowledge, universals, and ethics.)

Selected Secondary Literature in English

Allen, Julie, 1996, A Commentary on the Second Collatio of Peter Abailard’s Dialogus, Ph.D. Dissertation, Philosophy Department, University of Toronto.
Arlig, Andrew, 2007, “Abelard’s Assault on Everyday Objects”, American Catholic Philosophical Quarterly, 81: 209–227.
–––, 2012, “Peter Abelard on Material Constitution”, Archiv fur Geschichte der Philosophie, 94: 119–146.
–––, 2013, “Some Twelfth-century Reflections on Mereological Essentialism”, Oxford Studies in Medieval Philosophy, 1: 83–112.
–––, 2022, “Abelard and Other Twelfth-Century Thinkers on Social Constructions”, Philosophies, 7(4), 84. [Arlig 2022 available online]
Astroh, Michael, 2001, “Abelard on Modalities de re and de dicto”, in Potentialität und Possibilität. Modalaussagen in der Geschichte der Metaphysik, Thomas Buchheim, C. H. Kneepkens, and Kuno Lorenz (eds.), Stuttgart: Frommann Holzboog, 79–95
Bejczy, I., 2003, “Deeds Without Value: Exploring a Weak Spot in Abelard’s Ethics”, Recherches de théologie et philosophie médiévale, 70: 1–21.
Binini, Irene, 2022, Possibility and Necessity in the Time of Peter Abelard, Leiden/Boston: Brill.
Blackwell, Daniel, 1988, Non-Ontological Constructs: The Effects of Abaelard’s Logical and Ethical Theories on his Theology, Berne, Paris, New York: Peter Lang.
Boler, John, 1963, “Abailard and the Problem of Universals”, The Journal of the History of Philosophy, 1: 104–126.
Brower, Jeff, 1998, “Abelard’s Theory of Relations: Reductionism and the Aristotelian Tradition”, The Review of Metaphysics, 51: 605–631.
–––, 2004, “Trinity”, in The Cambridge Companion to Abelard, J. Brower and K. Guilfoy (eds.): 223–257.
Brower, Jeff and Guilfoy, Kevin (eds.), 2004, The Cambridge Companion to Abelard, New York: Cambridge University Press.
Freddoso, Alfred, 1978, “Abailard on Collective Realism”, The Journal of Philosophy, 75: 527–538.
Gracia, Jorge, 1984, Introduction to the Problem of Individuation in the Early Middle Ages, Washington, D.C.: Catholic University of America Press.
Guilfoy, Kevin, 1999, Abelard’s Theory of the Proposition, Ph.D. Dissertation, Philosophy Department, University of Washington.
–––, 2004, “Mind and Cognition”, in J. Brower and K. Guilfoy (eds.), 200–222.
Henry, D. P., 1985, “Abelard’s Mereological Terminology”, in Mediaeval Semantics and Metaphysics, E. P. Bos (ed.), Ingenium: Nijmegen, 65–92.
Hause, Jeff, 2007, “Abelard on Degrees of Sinfulness”, American Catholic Philosophical Quarterly, 81: 251–270.
Jacobi, Klaus, 1983, “Abelard and Frege: the Semantics of Words and Propositions”, in Atti del Convegno Internazionale di Storia della logica, V. Abrusci (ed.), Bologna: Ed. CLUEB, 81–96.
–––, 1986, “Peter Abelard’s Investigations into the Meaning and Function of the Speech Sign ‘Est’”, in The Logic of Being, Simo Knuutila and Jaakko Hintikka (eds.), Dordrecht: D. Reidel, 145–180.
–––, 2004, “Philosophy of Language”, in J. Brower and K. Guilfoy (eds.) 2004, 126–157.
King, Peter, 1982, Peter Abailard and the Problem of Universals in the Twelfth Century, Ph.D. Dissertation, Philosophy Department, Princeton University.
–––, 1992, “Peter Abelard (1079–1142)”, in The Dictionary of Literary Biography (Volume 115: Medieval Philosophers), Jeremiah Hackett (ed.), Detroit/London: Gale Research: 3–14.
–––, 1995, “Abelard’s Intentionalist Ethics”, The Modern Schoolman, 72: 213–231. [Preprint available online].
–––, 2004, “Metaphysics”, in The Cambridge Companion to Abelard, in J. Brower and K. Guilfoy (eds.), 65–125. [Preprint available online].
–––, 2007a, “Abelard on Mental Language”, The American Catholic Philosophical Quarterly, 81: 169–187.
–––, 2007b, “Abelard’s Answer to Porphyry”, in Documenti e studi sulla tradizione filosofica medievale, 18: 249–70. [Preprint available online].
Kretzmann, Norman, 1982, “The Culmination of the Old Logic in Peter Abelard”, in Renaissance and Renewal in the Twelfth Century, R. L. Benson and J. Constable (eds.), Cambridge, MA: Harvard University Press, 488–511.
Lenz, Martin, 2005, “Peculiar Perfection: Peter Abelard on Propositional Attitudes”, Journal of the History of Philosophy, 43: 377–386.
–––, 2007, “Are Thoughts and Sentences Compositional? A Controversy between Abelard and a Pupil of Alberic on the Reconciliation of Ancient Theses on Mind and Language”, Vivarium, 45: 169–188.
Lewis, Neil, 1987, “Determinate Truth in Abelard”, Vivarium, 25: 81–109.
Luscombe, David, 1969, The School of Peter Abelard, Cambridge: Cambridge University Press.
Mann, William, 2004, “Ethics”, in J. Brower and K. Guilfoy (eds.), 279–304.
Marenbon, John, 1997, The Philosophy of Peter Abelard, Cambridge: Cambridge University Press.
–––, 2006, “The Rediscovery of Peter Abelard’s Philosophy”, Journal of the History of Philosophy, 44: 331–351.
–––, 2013, Abelard in Four Dimensions: A twelfth-century philosopher in his context and ours, Notre Dame: University of Notre Dame Press.
Martin, Christopher J., 1986, “William’s Wonderful Machine”, Journal of Philosophy, 83: 564–572.
–––, 1987, “Something Amazing About the Peripatetic of Le Pallet”, Argumentation, 1: 420–436.
–––, 2001, “Abaelard on Modality: Some Possibilities and Some Puzzles”, in Potentialität und Possibilität. Modalaussagen in der Geschichte der Metaphysik, Thomas Buchheim, C. H. Kneepkens, and Kuno Lorenz (eds.), Stuttgart: Frommann Holzboog, 97–122
–––, 2004, “Logic”, in J. Brower and K. Guilfoy (eds.), 158–199.
Mews, Constant, 1987, “Aspects of the Evolution of Peter Abelard’s Thought on Signification and Predication”, in Gilbert de Poitiers et ses contemporains, J. Jolivet and A. de Libera (eds.), Naples: Bibliopolis.
–––, 2005, Abelard and Heloise, New York: Oxford University Press.
Pinziani, Roberto, 2003, The Logical Grammar of Abelard. Dordrecht: Kluwer Academic Publishers. (Translation of La grammatica logica di Abelardo, Parma 1992.)
De Rijk, L. M., 1980, “The Semantical Impact of Abailard’s Solution of the Problem of Universals”, in Petrus Abaelardus: Person, Wirk, und Wirkung, Rudolf Thomas (ed.), Trier: Paulinus-Verlag, 139–152.
–––, 1986, “Peter Abailard’s Semantics and his Doctrine of Being”, Vivarium, 24: 85–127.
Tweedale, Martin, 1976, Abailard on Universals, Amsterdam: North-Holland.
Wilks, Ian, 1993, The Logic of Abelard’s Dialectica, Ph.D. Dissertation, Philosophy Department, University of Toronto.
–––, 1997, “The Role of Virtue Theory and Natural Law in Abelard’s Ethical Writings”, Proceedings of the American Catholic Philosophical Association, 71: 137–149.
–––, 1998, “Peter Abelard and the Metaphysics of Essential Predication”, Journal of the History of Philosophy, 36: 356–385.
–––, 2008, “Peter Abelard and his Contemporaries”, in Handbook of the History of Logic (Volume 2: Medieval and Renaissance Logic), Dov Gabbay and John Woods (eds.), Amsterdam: Elsevier, 85–155.

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