For Descartes, according to Gueroult, “metaphysics” is the universal science or the system of science, and also a kind of introduction to more concrete studies. Here we are far from Aristotle and much closer, I think, to Duns Scotus. Without knowledge of God and oneself, Descartes says, it would never be possible to discover the principles of physics. Gueroult says that Descartes insists on an “incomprehensibility” of God that is neither unknowability nor irrationality but the “formal reason of the infinite” (Descartes selon l’order des raisons, p. 17). This again has a somewhat Scotist sound to my ear.
The infinitude of God puts God absolutely first, as the first truth that founds all others. Gueroult quotes Descartes saying, “It is a ‘blasphemy’ to say that the truth of something precedes God’s knowledge of it…, because the existence of God is the first and the most eternal of all the truths that can be, and the truth from which all the others proceed” (ibid; my translation).
Descartes says that God “freely creates” eternal truths. I have no idea what creation of eternal truths could even possibly mean, though such a notion seems to be at least implicit in the teaching of Duns Scotus. To be eternal is to have no before and after. Therefore, it seems to me, all eternal things must be co-eternal. This point of view accommodates part of Descartes’ thesis, insofar as if all eternal things are co-eternal, then an eternal truth would not “precede” God’s knowledge of it. In broadly neoplatonic terms, eternal truths could plausibly be regarded as aspects of the “nature” of God. I can also grasp the idea of truths following logically from the “nature” of God, but I suspect Descartes would either follow Scotus in arguing that God’s infinite power is not a “nature”, or follow Aquinas in arguing that God is pure existence and has no other “nature”. I don’t see how anything more specific can directly follow from either infinite power or pure existence.
For Descartes, though, God’s omnipotence “excludes the possibility of error” and “alone founds the objective validity of my intellectual faculty” (ibid). Descartes aims at “a total system of certain knowledge, at the same time metaphysical and scientific, … entirely immanent to mathematical certitude enveloped in the clear and distinct intellect, … in its requirement of absolute rigor. This totality of the system is in no way that of an encyclopedia of material knowledge effectively acquired, but the fundamental unity of the first principles from which follow all possible certain knowledge” (p. 18). Descartes’ doctrine is for him “a single block of certainty” (p. 19) that would be falsified by adding or removing any detail. All this seems way too strong to me.
Gueroult points out that Descartes wants to contrast an “order of reasons” with an “order of material”, as being more principled. However, unlike geometry, the total system of metaphysical reasoning for Descartes has “psychological” as well as logical requirements. Gueroult says it is for this reason that the Meditations best represent Descartes’ paradigm of rigorous analytic demonstration.
Granted that there is a clear “psychological” aspect to the Meditations, at this point I’m unsure what it means to relate that to the claimed rigor of the system. Moreover, adding a “psychological” dimension to what was said before about mathematical reasoning affects the very meaning of the claim of rigor. I think I understand what mathematical rigor is. I do not understand what “psychological” rigor would be in this context, but I suspect it may be wrapped up with what I would call extraordinary presumptions of absolute self-transparency and immediate reflexivity.