A Few Open Questions Concerning Some Common Cartesian Assumptions

Descartes concludes part five of his Discourse on Method as follows:

As to the rest, I elaborated here a little about the subject of the soul because it is of the greatest importance; for, after the error of those who deny the existence of God (which I believe I have sufficiently refuted), there is nothing that puts weak minds at a greater distance from the straight road of virtue than imagining that the soul of animals is of the same nature as ours and that, as a consequence, we have no more to fear nor to hope for after this life than have flies or ants

There are two features of this statement that I find puzzling, not only because Descartes puts them forward as obvious facts, but even more so because it seems many people today continue to hold to them. The first is that belief in the existence of God is tied in some special way to human exceptionalism and that to doubt the one is tantamount to doubting the other. The second is that emphasizing the commonality and continuity between human beings and other animals must necessarily mean “levelling down”, reducing humans to the debased status we assign to other animals, as opposed to lifting other animals out of their debased status.

What is it exactly that leads Descartes (and so many Christians today) to react to those who question the ontological distinction between humans and animals as if they were questioning the existence of God? From the perspective of Christian theology, isn’t there something deeply suspicious, almost idolatrous, about the way belief in human exceptionalism stands equal with belief in God? Moreover, why do so many Christians follow Descartes in assuming that to reject the categorical distinction between humans and (other) animals is to debase the human, even when the motivation for rejecting the distinction is explicitly to rethink the debased status we assign to other animals?