The ninth lesson is based on objections to dispositional monism that are sometimes undervalued, yet in our view major, and which have to do with confusions about necessitarianism and the interpretation of essentialism. Today, the confusion between essence and necessity (K. Fine) is commonplace, where we need to distinguish between :
Df1: F is a necessary property of a ssi a a F in all possible worlds that include a.
Df2: F is an essential property of a if being F is constitutive of theidentity of a.
Similarly, there is a tendency to obscure several possible meanings of the concept of necessity, preventing us from seeing that the intelligibility of dispositions undoubtedly lies more in the conditional necessity of the law, which in turn is only a true description of the world if it is based on what things can do, in the dispositional (and not just possibilistic) sense of the term.
The path of dispositional realism, which would give content to the project of a metaphysical knowledge of nature, is now clearer, and we have outlined its main features (which will be detailed in the seminar), which presuppose that we take into account the four theses presented in the seventh lesson.
We then drew a number of conclusions which, in our view, enable us to specify the metaphysical knowledge of nature we can legitimately hope to achieve. To do this, we first present some of the good arguments traditionally invoked in favor of humility: on the epistemic level, on the metaphysical level and on the semantic level (by Hume, Kant, but also, today, by metaphysicians convinced of the seriousness of metaphysics such as D. Lewis, or F. Jackson). At the other end of the spectrum, we find the arguments of those who seem to us to be moving from excessive humility to excessive audacity: such is the position of ontic structural realism or causal structural realism, whose merits but also whose limits we have assessed. Against the risk of idealism and holism, it seems to us desirable and possible to advocate, with dispositional realism, a "reasoned" humility that makes it possible to avoid "the dissatisfaction associated with any metaphysical commitment" (at least according to some, such as B. Stroud), while remaining aware, at least as much as of the limits of knowledge, of all that also escapes knowability (Fitch, P. Egré) and of all that, if we are to fulfill the program of an authentic "metaphysical knowledge of nature" remains to be done, for nature is certainly not limited to physical nature alone. The more detailed presentation of this program at the "Metaphysics and Science" symposium has already enabled us to compare these conclusions with the analyses of other contemporary metaphysicians (S. Psillos, A.S. Maurin, H. Beebee).
