Metaphysics of natural species (2)

However, for some contemporary essentialists (Kripke, Ellis [1]), this distinction between essence and necessary properties is unnecessary. Any property that a member of a given species cannot fail to have is an essential property of that species, and an essential property of a species is simply a property that no member of that species can fail to have. But is it enough for a property to be necessary (or a "rigid designator") to be essential? In short, is it enough to call a modal fact "essence" to make it ontologically more fundamental? Therein lies the question.

To gauge the scope of this question, we began by asking ourselves whether it was at all possible to know about natural species without knowing anything about their essence, with the help of a few forays into history, starting with the medieval period, which offers the double advantage of subtlety and complexity, by proposing, notably for the scotian response, several suggestions capable of testing the hypotheses of our dispositional realist model (which implied, in particular, recourse to what we had called a "thin essentialism" or "aliquidditism") (cf. last year's lecture). But the Subtle Doctor's (1265/66-1308) position on ENs is best understood as a reaction to Thomas Aquinas (1225-1274) or Henri de Gand (1217-1293) (characteristic of the position prevailing at the end of the ^13th century), which is where we started. Four major ideas guide these authors: individuals are indeed divided into EN. Those who are members of the same species have the same essence. The characterization of what is meant by "having in common", "sharing" or "same" essence, is rather elusive. Finally, the ultimate metaphysical foundation of these essences are the ideas found in the mind of God, models of the essences present in the world (Thomas Aquinas, Quodlibet VIII, q. 1). It's doubtful that we have cognitive access to these divine ideas, but that doesn't matter for knowing what ENs exist, and what their essences are, because we have non-inferential or direct access to them, through a simple act of cognition (or apprehension). As for common EN terms like "cats" or "human beings", they mean things as they are understood " res ut intellectae ".(ST I, q. 13, a. 2, ad 3). No need, then, for a distinction (which, for Locke, will be so important), between the nominal essence or meaning of our terms, and the real essence that has to do with the actual constituents of the world (Locke, Essay III. 3. 15, III. 6. 1-29). Terms signify real essences as grasped by our intellect through simple concepts obtained by abstraction from sensible individuals, by a first simple act ("apprehension"), followed by a second, consisting of our intellect composing into complex concepts what it has grasped in the first, and then by a third act, where it is a matter of reasoning from complex content through inferential reasoning. But such an approach is problematic: if all cognitive content comes to us from the intellect through the senses, and if only sensible qualities are the direct objects of the senses, then it is the superficial properties of species and accidents, not their essence, that reach us directly. Contrary to what St. Thomas says, then, we do not grasp real essences at all by an act of simple apprehension; we grasp them, if at all, not directly, but by an act of inference. The essential characteristics of any EN are in themselves unknown to us, and we describe them by recourse to concepts that are not simple but "complex". This is an awkward conclusion for Thomas Aquinas, because: 1) it runs counter to a thesis that he otherwise defends (and must defend because of his opposition to Averroism), namely that the proper object of the intellect is the quiddity of material things, in short, the essence of ENs. 2) It threatens certain key aspects of his epistemology, namely that it is impossible for the intellect to err in its grasp of essences; only simple acts of knowledge are safe from error, which is no longer the case when we elaborate complex concepts and make inferences(ST I, q. 85, a. 6). 3) And finally, a semantic problem: what do EN's terms actually mean, since words are supposed to signify things as they are understood by our intellect? All this is catastrophic in the context of an Aristotelian scientific project, where knowledge of the physical world imposes definitions of real essences. It's hardly surprising, then, that Thomas's successors set out to fill the gap that had now been created between, on the one hand, the ENs of the world, and on the other, the concepts and terms we have of them. And it is in this context that Duns Scotus' position takes shape and takes on its full meaning (on all this, see G. Pini's excellent analysis [2]).

The examination then turned to the way in which, first of all, from an epistemological point of view, Duns Scotus asks what we know about ENs, recalling the twofold interest, for our project, of two crucial points in the Scotian position: 1) the necessary distinction, inherited from Avicenna, of the metaphysical, epistemological and logical-semantic aspects of the EN problematic, and the indifferentiation of the "Common Nature", crucial in his response to the problem of universals, and for understanding the original turn of his essentialism) ; 2) affirmation of a form of unity of essences of ENs independent of the mind, based on the existence of "relations" not only of "resemblance" but also of "causality", between things in the world, as emphasized by our own model, which recalled the importance of "causal powers" as a criterion of a thing's identity.

However, while it is a given that real essences account for real relations such as resemblance or univocal generation, Duns Scotus admits that we have no simple concept of EN, since we only know directly the concepts of sensible accidents (red, hot, soft): only the intelligible species of these accidents are present to our intellect, and not the concepts of the substances that underlie them, the latter leaving no direct impression on our senses(Ord. I, d. 3, p. 1, q. 3, n. 138 (Vat. III, 87)). Or transubstantiation: all the bread's superficial sensitive properties remain unchanged - its color, taste and consistency continue to be there and felt. And yet, the essence of the bread is no longer there. If we stick, as we must, to what our senses teach us, denying the presence of bread is impossible. Whether the essence of bread is there or not, the content of our thoughts that reaches us through the senses is the same. But to know is also to know when something isn't there, which in this case doesn't seem to be the case, since our intellect is incapable of telling us when the substance that is bread isn' t there. This sheds some light on our knowledge of substances: if God were to destroy one of them, leaving only the superficial sensible properties, our concept would remain unchanged. Conversely, if God were to destroy all sensible accidents and leave only the substantial essences that underlie them, we would be equally unable to identify any of these essences, since we can only identify a substantial essence by virtue of its accidents. So two people can have the same thought about a certain thing, even if one of them has never been exposed to it. This is what Duns Scotus is going to demonstrate by means of a thought experiment that (despite the different conclusions that each person draws from it) is reminiscent of the one later taken up by an author like Putnam (the twin-earth experiment).

[1] Ellis B., Scientific Essentialism, Cambridge, Cambridge University Press, 2001.

[2] Pini G., "Scotus on Knowing and Naming Natural Kinds", History of Philosophy Quarterly, 26, 2009, 255-72.