musing on Cartesian causation

Here’s a brief meditation on Descartes’ views of causation.

For Descartes’ teachers, the causal alterations of the material world were to be explained by reference to substantial forms. These were the entities that were the causal relata invoked to explain alteration, generation, and corruption.

For many reasons, Descartes came to reject the explanatory value of substantial forms (chief among the reasons, other than the obvious issues concerning mechanistic physics: he considered them to be crass reifications of concepts and hence a huge mistake in metaphysics), but he ended up replacing them with God. There is therefore some truth to the claim that for Descartes God becomes a sort of deus ex machina, at least by our standards of explanation.

Quick points:

1. Descartes affirmed occasionalism (i.e., denied genuine causal powers to material bodies) for body-body causal relations. God is the real and sole cause of alterations in causal phenomena involving bodies and other bodies. [Philosophical aside: What motivated occasionalism? The quick answer is a combination between (a) a pious but overwrought view of divine omnipotence/providence and (b) constrained perspectives on what it would take for passive matter to be affected.]

2. Descartes affirmed genuine causal powers of finite minds to cause alterations in material bodies, in most cases, the body intimately connected to one’s own mind. This is what primarily distinguishes him from the pure occasionalists (such as Malebranche).

3. It’s not clear what Descartes believed about body-mind causal relations. Specifically, he doesn’t seem to have a consistent story to tell about whether or not material bodies cause sensations in minds.

In the Meditations, Descartes appears to commit himself to the view that the ideas of material bodies are genuinely caused by those very bodies that stand outside of the mind. His distinction between innate and adventitious ideas appears to require such a view.

However, in the later Principles, there’s a key entry in the French edition that reads as follows: “...it seems to us that the idea we have of it forms itself in us on the occasion of bodies from without (Principles II.1).”

If we throw into the mix his real views on the radical innateness of ideas, then I think a picture emerges in which Descartes is probably best thought of as a semi-occasionalist with respect to body-mind causal relations.

For Descartes, all ideas are innate, not just the “big” ones like the idea of God, geometry, or the infinite. Even sensory ideas are innate, as he makes explicit in his Notes on a Certain Broadsheet. Here’s a quotation: “Hence it follows that the very ideas of the motions themselves and of the shape are innate in us. The ideas of pain, colors, sounds, and the like must be all the more innate if, on the occasion of certain corporeal motions, our mind is to be capable of representing them to itself, for there is no similarity between these ideas and the corporeal motions.”

I call this semi-occasionalism because strictly speaking God is not the direct cause of these sensations in a way that is isomorphic with the way in which God is the direct cause of motions in the case of body-body causation.

In this special case of body-mind causation, there is a kind of active principle (a dispositional structure or set of properties) in the soul that, under the right activation conditions, produces all the various ideas—sensory and otherwise. [Another philosophical aside: This is what distinguishes Descartes from being a recollectionist-nativist such as Plato.] The activation conditions are the occasions (of brain stimulation or whatnot) for the dispositional properties to manifest their characteristic expressions. The important things are (a) the relation between the external stimuli and the manifestations (i.e., the mind’s ideas) is non-causal and (b) the relation between the dispositions and the expressions is causal (but that sounds odd too... do dispositions “cause” their manifestations?).

It’s in this sense that it’s semi-occasionalism: God is only involved in an indirect sense in which he is the one who created and placed those dispositions in the soul in the first place, but then they take on a kind of causal independence of their own in their occasionalist brokering of representational relations between mind and world.