Encyclopedia of Medieval Philosophy

2011 Edition
| Editors: Henrik Lagerlund

Peter of Ailly

  • Joël Biard
Reference work entry
DOI: https://doi.org/10.1007/978-1-4020-9729-4_384


Peter of Ailly was one of the most important thinkers and philosophers of the later fourteenth and the early fifteenth century. He was deeply involved with the Papal politics of his time and wrote several philosophical works that remained influential well into the sixteenth century.

Peter of Ailly was born in 1351 in Compiegne. His philosophical background was formed from 1364 onward at the College of Navarre. He obtained his Arts degree in 1367, and joined the Faculty of Theology from which he graduated in 1381. He then became Regent Master. He was appointed Grand Master of the College of Navarre in 1384 and then Chancellor of Paris University in 1389.

From this time on Peter of Ailly was involved in the struggles surrounding the Great Western Schism, which divided Europe between 1378 and 1414. After the return of Gregory IX to Rome, the College of Cardinals, reduced in number, convened to elect a Pope. But later it was argued that it had acted under pressure and another Pope was elected. From that time on there existed two opposed series of Popes, one in Rome and another in Avignon. It was only with the Council of Constance in 1414–1418 that the schism ended.

In 1381, Peter of Ailly became the voice of a group of students who demanded a council to put an end to the schism. After having published a pamphlet (Epistola Leviathan), he was forced to flee to Noyon, but then returned to Paris in 1384. He is involved in fights against the Chancellor of the university, which was forced to resign in 1385, and against the Dominicans. He became the Chaplain of King Charles VI. He then argued in support of the Popes of Avignon. He became Bishop of Le Puy, and then Bishop of Cambrai in 1396. He experienced both good times as the time when he in 1403 was the ambassador of the King to Benedict XIII in Avignon, and moments of difficulty during which he devoted himself to his diocese, as for example when he in 1408 had to take refuge in Cambrai. Peter of Ailly was appointed Cardinal in 1411 and Papal legate in Avignon of Pope John XXIII in 1413. He participated in the Council of Constance that marked the end of the schism with the election of Martin V, and the resignation of the Pope of Rome and the deposing of others. During this same council, he took an active part in the conviction of John Huss. He spent the remaining years of his life in Avignon, where he died in 1420.

Peter of Ailly was a great scholar. He possessed a very extensive library, and was associated with early French humanists. He wrote a considerable number of books (about 170 are known). His philosophical works include a Tractatus de anima, written between 1377 and 1381, and a Tractatus de consolatione philosophiae Boethii, dating from the same period. He also wrote the Conceptus, which gives an exposition of the different kinds of conceptual terms and their organization in the early 1370s, and a treatise on the Insolubilia (between 1372 and 1375) dealing with the truth and falsity of propositions in general, and self-reflexive propositions in particular. There is also a Tractatus exponibilium, in six chapters, written between 1384 and 1388, outlining, in a systematic fashion, propositions with adverbial or syncategorematic terms in such a way that they should be explicitly explained by several underlying propositions. The authenticity of the treatise De destructione modorum significandi has been challenged but is now accepted. It was written before 1388. His Questions on the Books of the Sentences (read in 1376–1377) manifests the trend of the fourteenth century to reduce the number of issues dealt with, then to amplify them and insert many strictly philosophical developments. All these works were widely circulated up until the early sixteenth century.

His Imago mundi, a geography text, is still famous because Christopher Columbus owned a copy of it. But this is mostly a compilation made from ancient authors, in particular Ptolemy. He also composed a dozen other cosmographic, astronomical, and astrological works. In the latter, he defends the validity of astrology as a study of the influence of the stars on the course of human history.

Among his ecclesiological and political works, two works from his mature period should be mentioned, namely the Tractatus de materia concilii generalis (1402–1403) and the Tractatus de ecclesiastica potestate (1416), as well as a small compendium written for the Council of Constance, Tractatus de reformatione Ecclesie. He is also the author of many sermons in both Latin and French.

In logic and philosophy of language, Peter of Ailly manifests the influence of Ockham’s philosophy in Paris. He gives all his attention to the theory of mental language. William of Ockham represents a major turning point in treating the domain of concepts as a true language, subject to a principle of compositionality, governed by syntax, and bearing semantic properties. According to Peter of Ailly, the level of concepts, organized into a language, is the major area, if not the only, of all logical, semantic, and epistemological analysis. The division and classification of the types of terms, by which logic usually begins, becomes a classification of concepts, that is, into simple or complex, absolute or connotative, but also into categorematic or syncategorematic, nominal or verbal, adjectives or substantives, etc. All logical and grammatical differences within spoken language are dependent on differences in mental language. This is why Peter of Ailly, in the Conceptus, and in the Destructio modorum significandi, denies that there are principles of construction of spoken language, which was the function performed by the “modes of signifying” of speculative grammar. The construction or the grammatical “regimen” results from the conventional subordination of spoken terms to concepts, which are by themselves ordered in a certain way. But we have to make a distinction, which Peter of Ailly picks up from Gregory of Rimini, between mental language improperly speaking, which is only the mental image of the spoken language, and is as such conventional, and mental language properly speaking, which is the determining structure of the semantic properties and the epistemological significance of language. A simple apprehensive cognition is the mental term itself, which is a concept and which naturally signifies something.

In this context, there is no room for the idea, developed in Oxford in the late 1320s and made famous in Paris by Gregory of Rimini in the 1340s, of the “proper and adequate significate of the proposition.” In the Commentary on the Sentences (Book I, Dist. 35, q. 1), this issue is discussed regarding the compatibility between the divine science and the contingency of the future. Paradoxically, as often, the general framework is dependant on Gregory of Rimini’s commentary. Some future contingents are incomplexe significabilia, that is, they are possible entities, which will possibly be expressed in the future. But are the complex enunciables that can be expressed in the present about the future, complexe significabilia as some believe? Peter states that they are rather complexe significantia. The whole complexity is then located in the significant complex expressions and not in the significates. He then deviates from Gregory and returns to a Buridanian position in which only individual things are signified, and in which these are signified either in a simple or in a complex manner. The only other difference that we find in the Conceptus is that terms are also signifying aliqualiter, in a certain way. In fact, according to an expression that we shall find again, for example, in the early sixteenth century in John Mair, concepts signify “aliquid vel aliqua vel aliqualiter.” They can signify one thing or several things or in a certain way, somehow, in the case of syncategorematic terms, given that there are mental syncategorematic terms. This kind of signification is not only a modification of the signification of categorematic terms, of the direct reference to some entitates, not just a way of signifying, but it is the adverbial signification of mental syncategorematic terms. In the Insolubilia, Peter of Ailly is very harsh on the theory of complexe significabilia that he considers to be “irrational and unintelligible.” He rehashes a Buridanian argument, namely that all that there is, is either one thing or nothing, either a substance or an accident, either God or the creation, and the complexe significabile can in no way be situated in this scheme. In the same treatise, Peter of Ailly admits that some propositions, since they are self-reflective, signify something about themselves, for example, they signify that they are false. He refuses, however, the generalization proposed by Thomas Bradwardine in his own Insolubilia that any proposition implicitly signifies its own truth or falsity.

The relation of a cognitive power to an object is called a notitia. The different kinds of cognitions are discussed in the Tractatus de anima. A notitia can be both sensitive and intellective. That which is known or knowable is called an obiectum. But the object is not an intentional being distinct from the thing. It is the thing itself as it is in front of the cognitive power. Every thing is not ipso facto an object, but it is as far as it is directed to a cognitive power, at least in the case of a present thing. In the case of past or future things, or things simply absent from my field of apprehension, it is an image, a species, which takes the place of the object so that the cognitive power can perform its function. The concepts or notitie are acts of the intellect, characterized as immutatio vitalis, vital actions or changes. In the Commentary on the Sentences, we find as a general definition: “a cognition is an act representing something in a vitally perceptive power.” Speaking of acts implies refusing any idea of a concept as mental content. This is why the model here is that of a direct relationship, not that of mediation by a representation.

The question of the intermediate, however, reappears together with the distinction between intuitive and abstractive cognition. In his Commentary on the Sentences (Book I, q. 3), Peter of Ailly defines first of all an abstractive cognition as one that abstracts from the existence or nonexistence of the thing, while an intuitive cognition cognizes it as present, according to its actual existence. Furthermore, he insists on the fact that an abstractive cognition gives us the object “in a thing which represents it.” Agreeing with the definitions of Gregory of Rimini, which is close to Scotus, Peter of Ailly outlines, in the Commentary on the Sentences and in the Treatise on the Soul, intuitive cognition as that by which something is known formally in itself, whereas abstractive cognition is that by which something is known through a representation.

This idea leads (especially in the Insolubilia) to a distinction between formal and objective signification. The first is that by which a concept refers itself to the thing it signifies, the second explicates the mediation through which a cognition or a concept refers to something. This intermediate being is like an image (species) or a spoken sign. This duality between formal and objective signification will later be crossed with the idea of an objective or intentional being. Then it will be found in the theory of formal and objective concepts at the end of the sixteenth century.

The Commentary on the Sentences is also famous for strictly theological reasons, particularly regarding its doctrines of predestination and justification, which are known until the sixteenth century. The absolute simplicity of the divine being prohibits all distinctions within it, whether it be that of faculties or ideas. The order of established secondary causes is contingent. It is the level of ordained power. But by his absolute power, God can directly do what he ordinarily does by the secondary causes. This applies to the sacraments as well as to grace. In the established order, the habit of created charity, freely given by God, is necessary to avoid sin, although de potentia absoluta the one does not imply the other. Prescience of merits is not the cause of justification, because justification is unmotivated. But in the established order, sin is the cause of reprobation. Our concept of God is obtained by an abstractive cognition from what is created. If we cannot have an evident cognition of God we have, however, a probable (probabilis) cognition of him. Peter of Ailly’s probabilism is equally invested in theology and philosophy. This does not lead to fideism, and a fortiori certainly not to skepticism. Absolute evidence is limited to the noncontradictory and (according to the ordained power) to the intuition of what exists, but reason gives us relative certainty and conditional evidence in the natural order of ordained power, in which causal relationships, such as the commandments, are contingent, and the same hold in matters of Trinitarian theology.

The Treatise on the Consolation of Philosophy of Boethius is presented as a work of moral philosophy. It includes a eulogy of philosophy in the beginning, and ends with a part on future contingents. But the main problem is that of happiness. Peter wonders if a philosopher can attain true happiness through natural means. He develops a purely philosophical approach. However, the philosopher reaches only a probable cognition. Peter of Ailly does not adopt, even as a relative truth, the doctrine of intellectual happiness, and he has reservations about the Aristotelian theory formulated in the Nicomachean Ethics. At the same time, he revisits the position of Scotus, accentuated by Ockham, that faith is required for understanding the true good. Peter admits the existence of a human tendency toward the ultimate good, a summum bonum. And he even recognizes, through a convincing argument, that God is the summum bonum. However, the supreme good cannot be attained by a human being in this life, since only God gives happiness through the beatific vision.

Peter of Ailly does not develop a real political philosophy, but political theories are present in his ecclesiological work. These are marked by the context of the Great Schism, and his position in favor of a council to resolve the crisis. He supports the distinction of civilian and spiritual power whose purposes are different. The spiritual power is superior in dignity but does not exercise the prerogative upon civil power. It is the universal Church, not the Pope, that has the “fullness of power.” He often takes on the ideas of John of Paris, and he applies the Aristotelian analysis of the ends of the government to the Church. The political authority must ensure the good of the community as a whole. The Council does not have to judge the Pope, but if the survival and unity of the Church is no longer secured with the Pope, the General Council becomes the representative of the Church. The source of authority is the consent of the community.

The most famous pupil of Peter of Ailly was John Gerson, but Peter exerted a widespread influence for two centuries in philosophy of language, theology, and political ecclesiology. He was for a long time viewed negatively, but his ideas are now revalued thanks to a better understanding of what absolute power means as well as a more measured assessment of his doctrines of grace and justification. His works are seen as important sources for understanding the logic and the epistemology of his century.

See also:  Future Contingents;  Gregory of Rimini;  Insolubles;  Intuitive and Abstractive Cognition;  John Buridan;  John Duns Scotus;  John Mair;  Mental Word/Concepts;  William of Ockham


Primary Sources

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Authors and Affiliations

  • Joël Biard
    • 1
  1. 1.Centre d’Etudes Supérieures de la RenaissanceUniversité François-Rabelais de ToursToursFrance