Charles Ehret

In thirteenth-century philosophical psychology, it is commonly held that the powers of the soul, responsible for a living being’s various operations, “flow” from the soul’s essence. The phrase is used systematically by Albert the Great, who imports it from Avicenna. It suggests that the soul, considered as a separate substance, is ontologically distinct from its powers. This is how Albert understands Avicenna, and how modern interpreters understand both Avicenna and Albert. The aim of this paper is to call into question such an understanding, as a reading of Avicenna and as a philosophical doctrine. It argues that an ontological distinction between the soul and its powers isn’t intended in Avicenna, and isn’t successfully established in Albert. It further argues that psychological emanation yields such a distinction only in Aquinas, where the soul is no longer considered a separate substance, but a material form.

For Aquinas, a concept is about something only if it relates to the common nature of a particular being attended to through perception. Intentionality is fundamentally perceptual for Aquinas. Having argued this claim, I then give a novel account of perceptual intentionality in Aquinas, according to which the forms received by perceivers (“sensible species”) are the same particular forms as those in the perceived object. This is possible because accidental forms have two individuators: matter makes them particular and quantity makes them distinct. Aquinas’s claim that sensible species are “without matter” implies that, although they are distinct from the perceived qualities, they remain the same particular forms. This allows us to say that one has a distinct view of this particular object, which accounts for the intentionality of perception, and thus for the intentionality of concepts, as applied to what is perceived.

Aquinas claims against Avicenna’s causal determinism that even a sufficient cause can be impeded. I analyze Aquinas’s claim in the context of his reading of Aristotle’s Metaphysics (VI 3) and argue that it ultimately rests on the idea that no cause has the per se effect of disposing matter to form. A cause can thus be impeded by the indisposition of matter while being sufficient for the production of form. By contrast, Avicenna understands that the per se effect of natural causes is precisely to dispose matter, thus accounting for the removal of impediments, and this is why, I argue, there is no sense in which a sufficient cause can be impeded on Avicenna’s view.

This paper studies the distinction between the essence of the soul and its powers in Thomas Aquinas as it develops from a theological to a psychological claim. A reconstruction of this development will show that the distinction is initially foreign to Aristotle’s philosophical psychology and leads Aquinas to break away from Aristotle’s conception of form. Ultimately, the distinction is postulated for its theoretical benefit, as it allows Aquinas to explain how the intellect can be a non-bodily power of a bodily form – something other authors of the Aristotelian tradition can difficultly account for.

La Physique d’Aristote est travaillée par un problème souterrain. D’après ses principes, ce qui est mû ne saurait mouvoir : un mû est en puissance et un moteur est en acte, de sorte qu’un moteur essentiellement mû est une contradiction. Le présent livre montre l’importance de ce problème dont la solution n’apparaît qu’avec le concept d’instrument élaboré au XIIIe siècle par Thomas d’Aquin. Si l’instrument chez Thomas correspond au « moteur mû » aristotélicien, l’Aquinate ne s’en tient pas à cette formule lorsqu’il produit une théorie détaillée de la causalité instrumentale. À l’analyse, la notion de moteur mû se dissipe et l’instrument apparaît comme ce qui agit en vertu d’un autre. Cela signifie que l’agent principal donne son pouvoir (virtus) à l’instrument, qui le reçoit selon un être intentionnel (esse intentionale). Cette doctrine délicate ne se comprend qu’à condition de restituer la physique qu’elle dépasse et la métaphysique des pouvoirs à laquelle elle aboutit.

The following paper proposes a critical reading of conventionalism in sacramental theology (“causalité-pacte”), to underline, by contrast, the theoretical merits of its main competitor, Aquinas’s instrumental causality. It shows that conventionalism, to make the sacrament truly efficient, assigns to the sacrament itself the power of convention, a power compared to the royal seal, which is naturally efficacious qua effect formally identical to its cause. This supports Aquinas’s conviction: rules are powerless, only things have powers.

In thirteenth-century philosophical psychology, it is commonly held that the powers of the soul, responsible for a living being’s various operations, “flow” from the soul’s essence. The phrase is used systematically by Albert the Great, who imports it from Avicenna. It suggests that the soul, considered as a separate substance, is ontologically distinct from its powers. This is how Albert understands Avicenna, and how modern interpreters understand both Avicenna and Albert. The aim of this paper is to call into question such an understanding, as a reading of Avicenna and as a philosophical doctrine. It argues that an ontological distinction between the soul and its powers isn’t intended in Avicenna, and isn’t successfully established in Albert. It further argues that psychological emanation yields such a distinction only in Aquinas, where the soul is no longer considered a separate substance, but a material form.