D’Ailly was a prolific writer on a number of subjects. His best known philosophical works concentrate on logic and on faith and reason, with strong influences from Ockham in particular. He also wrote influential works on the nature of the soul. He was one of the most eminent partisans of the late medieval nominalist movement and was numbered among the foremost doctores renovatores by King Louis XI in his decree against the nominalists. His works continued to be highly influential as late as the Reformation period.
Pierre d’Ailly, rector of the Collège de Navarre, chancellor of the University of Paris, bishop of Le Puy and Cambrai, cardinal and papal legate to Germany, was a man of wide interests and inexhaustible energy. He wrote a great number of treatises on the most varied subjects, besides performing the many duties associated with his ecclesiastical and secular posts. He left behind over one hundred and seventy works; those devoted to purely philosophical matters are few in number and were all written in the early years of his academic career, while he was teaching philosophy at the Collège de Navarre. The largest group of his works is devoted to matters relating to the Great Schism (during which there were two, or even three, popes) which endured for almost forty years. After the beginning of the Schism in 1378, d’Ailly concentrated on finding a way to terminate this horrenda
monstruosaque divisio (abhorrent and monstrous division) and was completely distracted from philosophy.
His influences were widespread and lasting. Martin Luther was substantially influenced by d’Ailly’s theory of the Eucharist (developed in the fourth book of his Commentary on the Sentences, written in 1376-7). In his own treatise De captivitate Babylonica ecclesiae (The Babylonian Captivity of the Church), Luther recalls:
Once, during my study of scholastic theology, Pierre d’Ailly gave me occasion to think (while I was reading his fourth book on the Sentences, where he argues most acutely) that it would be much more probable, and one would need fewer of those superfluous miracles, if one would affirm that on the altar there were real bread and real wine, not just their attributes - if the Church had not determined the opposite. When I later realized which Church it was that had determined this - the Thomistic Church, to be sure - I became more courageous.
(De captivitate Babylonica ecclesiae) Christopher Columbus owned d’Ailly’s geographical works Imago mundi (The Appearance of the World) and
Epilogus mappae mundi (Epilogue on the Map of the World), both written in 1410. They influenced Columbus in
his search for a shorter sea route to India and consequent discovery of America; of the authors Columbus had studied, it was d’Ailly whom he preferred to quote. Nicholas of Cusa used d’Ailly’s Exhortatio super kalendarii
correctione (On Corrections to the Calendar), written in 1411 for Pope John XIII and later publicly read at the
Council of Constance, for his own treatise De correctione kalendarii. In his Exhortatio, d’Ailly advocated - in vain - the reform of the calendar that was later successfully promulgated by Pope Gregory XIII. Johannes Kepler, himself an apologist for a reformed astrology, explicitly refers to d’Ailly’s astrological works in his treatise De
stella nova in pede Serpentarii (The New Star in the Foot of the Serpent); in one of those works, the Elucidarium astronomicae concordiae cum theologica et historica veritate (On the Concordance of Astronomy with Theology and Historical Truth), written in 1414, one finds the first mention of d’Ailly’s famous prediction of the French
Revolution, which he repeated in his treatise De persecutionibus ecclesiae (The Persecutions of the Church). Much of fourteenth-century thought is characterized by a desire to disengage faith from reason and to build upon empirical facts rather than metaphysical assumptions. Thus, it is not by chance that two of d’Ailly’s favourite phrases in his philosophical writings are docet experientia (experience teaches) and patet inductive (this is clear on the basis of induction). His main sources are William of Ockham, Thomas Bradwardine, Gregory of Rimini and John Buridan, among whom Ockham is clearly the foremost authority: ‘a few things said by him I value more highly than many volumes by certain others’ (Tractatus de consolatione philosophiae Boethii, q.1, art.4: 132). Pierre d’Ailly’s logical writings - Conceptus (Concepts), Insolubilia (Insolubles), Exponibilia (Exponible Propositions) and Destructiones modorum significandi (Attacks on the Modes of Signifying) (of dubious
attribution) - were very influential in the later Middle Ages and through the fifteenth century. D’Ailly adheres to the Ockhamist tradition in basing his logical theories on the notion of mental language. Concerning paradoxes of self-reference (insolubilia), for instance, he holds that there are none in mental language, and that spoken or
written paradoxes of this sort are ambiguous sentences in so far as they correspond to two distinct mental
sentences, one true and the other false (see Language, medieval theories of §§2, 3, 14). It is worth noting that the term vitalis immutatio (vital change) plays an important role in d’Ailly’s definitions of central logical terms such as conceptus and significatio, which are thus closely connected with his theory of the soul and its powers. His Tractatus de anima (Treatise on the Soul), certainly one of the most important systematic works on
philosophical psychology written in the fourteenth century, was widely read throughout the fourteenth, fifteenth and sixteenth centuries. Gabriel Biel wrote a valuable commentary on it. The first chapter deals with the definition of the soul and its tripartite division, chapters 2-8 deal with the powers of the vegetative, sensitive and intellective soul, while the concluding seven chapters deal with the accidents of the soul: species, the acts of sensation,
intellection, volition and passion, and habits. D’Ailly’s definition of the soul deviates from Aristotle’s formulation: ‘The soul is the substantial form of a living body that has within it the capacity to carry out vital activities’. This definition of the soul was adopted by other late medieval authors such as Symphorien Champier (see Soul, nature and immortality of).
D’Ailly’s Tractatus super De consolatione philosophiae Boethii (Treatise on Boethius’ Consolation of Philosophy) is mainly devoted to the theory of human happiness. Whether a human being can be called ‘truly happy in this life’ was one of the central ethical questions in the Buridanist school, where the term homo
felicitabilis (the human being with a capacity for happiness) was coined. In this context, d’Ailly also discusses the
question of immortality. In Tractatus de anima, he had followed Buridan in affirming that if one follows human reason alone, then Alexander of Aphrodisias’ theory of the soul - that the human soul is ‘drawn from matter’s potentiality’ and hence mortal - is the most probable (see Alexander of Aphrodisias). But in Tractatus de anima, he strongly opposes Alexander and, while relying heavily on arguments taken from ancient authorities like Cicero and Seneca, sides with Nicole Oresme in declaring that even ‘in accord with the light of nature’, the immortality of the soul is more probable.
See also: Nicholas of Cusa; Soul, nature and immortality of the; William of Ockham
OLAF PLUTA List of works
D’Ailly, Pierre (1350-1420) Conceptus (Concepts), ed. J. Biard, L. Kaczmarek and O. Pluta, forthcoming; trans. P.V. Spade, Peter of Ailly: Concepts and Insolubles, Dordrecht: Reidel, 1980.(D’Ailly’s writings on logic.) D’Ailly, Pierre (1350-1420) Insolubilia (Insolubles), ed. J. Biard, F. Del Punta, L. Kaczmarek and O. Pluta,
forthcoming; trans. P.V. Spade, Peter of Ailly: Concepts and Insolubles, Dordrecht: Reidel, 1980.(D’Ailly’s writings on logic.)
D’Ailly, Pierre (1350-1420) Exponibilia (Exponible Propositions), ed. J. Biard, L. Kaczmarek and O. Pluta, forthcoming.(D’Ailly’s writings on logic.)
D’Ailly, Pierre (1350-1420) Destructiones modorum significandi (Attacks on the Modes of Signifying), ed. L. Kaczmarek, Amsterdam: Grüner, 1994.(Dubious attribution.)
D’Ailly, Pierre (1350-1420) Tractatus de anima (Treatise on the Soul), in O. Pluta (ed.) Die philosophische Psychologie des Peter von Ailly, Amsterdam: Grüner, 1987.(Follows Buridan in supporting the views of
Alexander of Aphrodisias.)
D’Ailly, Pierre (1350-1420) Tractatus super De consolatione philosophiae Boethii, in M. Chappuis (ed.) Le Traité de Pierre d’Ailly sur la Consolation de Boéce, Qu. 1, Amsterdam: Grüner, 1993.(Discusses the theory of
human happiness.)
References and further reading
Biard, J. (1992) ‘Présence et représentation chez Pierre d’Ailly: Quelques problèmes de théorie de la
connaissance au XIVe siècle’ (Presence and Representation in the Work of Pierre d’Ailly: Problems of the Theory of Knowledge in the Fourteenth Century), Dialogue 31: 459-74.(Expounds and discusses d’Ailly’s theory of knowledge as found in his Commentary on the Sentences and his philosophical writings.)
Chappuis, M. (1984) ‘Notice sur le Traité de Pierre d’Ailly sur la Consolation de Boèce’ (Review of Pierre d’Ailly’s treatise on the Consolation of Boethius), Freiburger Zeitschrift für Philosophie und Theologie 31: 89-107.(Examines all the extant manuscripts of the Tractatus super De consolatione philosophiae Boethii and gives a summary of its contents.)
Chappuis, M., Kaczmarek, L. and Pluta, O. (1986) ‘Die philosophischen Schriften des Peter von Ailly. Authentizität und Chronologie’ (The Philosophical Writings of Pierre d’Ailly: Authenticity and Chronology),
Freiburger Zeitschrift für Philosophie und Theologie 33: 593-615.(Disputes the authenticity and chronology of
d’Ailly’s philosophical writings, including the Destructiones modorum significandi.)
Kaczmarek, L. (1990) ‘Vitalis immutatio. Erkundungen zur erkenntnispsychologischen Terminologie der Spätscholastik’ (Lively Changelessness: Explanations of the Epistemological Terminology of Late Scholasticism), in A. Heinekamp, W. Lenzen and M. Schneider (eds) Festschrift für Heinrich Scheper,
Münster: Nodus, 189-206.(Analyses the use of the term vitalis immutatio in John of Ripa’s Commentary on the
Sentences and argues that d’Ailly has adopted this term from him.)
Nuchelmans, G. (1973) Theories of the Proposition: Ancient and Medieval Conceptions of the Bearers of Truth and Falsity, Amsterdam: North Holland, 259-65.(Gives an outline of d’Ailly’s theory of the proposition in his Commentary on the Sentences, Conceptus, Insolubilia and the (dubious) Destructiones modorum significandi.) Ouy, G. (1975) ‘Le Collège de Navarre, berceau de l’humanisme français’ (The Collège de Navarre, Cradle of
French Humanism), Actes du 95e Congrès National des Sociétés Savantes de Paris et des Départements, Sect. de Philologie et d’Histoire, Reims 1970, vol. 1, Paris: Bibliothèque nationale, 275-99.(Shows that the College of Navarre was the cradle of French humanism, its foremost representatives being the ‘Navarristes’ Pierre d’Ailly and Jean de Montreuil, and later Jean Gerson and Nicolas de Clamanges.)
Pluta, O. (1990) ‘Die Diskussion der Frage nach der Unsterblichkeit bei Nikolaus Oresme und Peter von Ailly’ (The Discussion of the Question of Immortality in Nicole Oresme and Pierre d’Ailly), Studia Mediewistyczne 27 (2): 115-30.(Expounds and discusses the question of immortality as found in Nicole Oresme’s Quaestiones
de anima and d’Ailly’s Tractatus de anima and Tractatus super De consolatione philosophiae Boethii.) Spade, P.V. (1980) Peter of Ailly: Concepts and Insolubles, An Annotated Translation, Dordrecht: Reidel.(The
introduction (1-15) presents an introduction to the main topics of Conceptus and Insolubilia with special emphasis on d’Ailly’s sources.)