Was Aquinas a property dualist?

Was Aquinas a property dualist?

E.Feser

But what about human beings, you ask?  Doesn’t Aquinas think of them as material substances with immaterial properties?  I’m inclined to say that that is not quite his view, or not quite what his view should be, given his broader metaphysical principles.  This is where the neglected option that contemporary philosophers of mind might have seen, but seem not to, comes in.  The idea of a material substance with both material and non-material properties is only one of two possible ways of spelling out property dualism.  Another way of doing so would be in terms of the idea of an immaterial substance with both material and non-material properties.  And that, I suggest, is essentially what Aquinas took a human being to be.

As I have argued elsewhere, most recently in an essay for the Blackwell Companion series, the Thomistic thesis that the soul is the form of the body is often misunderstood.  Many people read it as saying that the soul is the form of a substance that is entirely bodily, just as the soul of a dog or a tree is the form of a substance that is entirely bodily.  Then they find it puzzling that Aquinas could go on to say that the human soul subsists after death.  For how could the human soul continue after death if it is the form of the body and the body is gone, any more than the soul of a dog or of a tree could subsist after death?

But this misunderstands the Thomistic thesis.  The human soul is the form of a substance which has both bodily operations (like breathing, walking, seeing, etc.) and non-bodily ones (like thinking).  Because it is what gives the substance in question the bodily operations in question, it is, naturally, the form of the body.  But it doesn’t follow that the substance in question is entirely bodily, the way that a dog or a tree is.  It is not.  Even when alive, part of what we do (thinking and willing) isn’t entirely tied to the body in the first place.  That’s why the death of a human being does not entail his annihilation.  He carries on in a highly truncated state, reduced to his intellect and will – as an incomplete substance, as Aquinas says. 

And what kind of incomplete substance is that?  An immaterial one, naturally, since the body is gone....