An act of will is “determined” in Descartes’ sense just in cases where an external force directly determined the act of the will. If the act of the will is determined by internal forces then the act, according to Descartes, is not determined. When I first read this, it struck me as a bit strange, but I was not able to figure out what it was that was unusual. Ragland’s diagram on page 386 of “Descartes on the Principle of Alternative Possibilities” made me realize that acts of will determined by internal forces are often no less determined than acts of the will directly determined by external forces. Including internal forces does nothing more than add one more link to the chain.
If a person’s internal forces are entirely determined by some external force, then the resulting act of will could end up being exactly the same as an act of will determined directly by some external force. In many cases, adding a link between the external forces and the act of will does not seem to change the causal story enough to warrant saying that act of will is now not determined by the external forces indirectly acting upon it.
Let us suppose that internal force (I) brings about act of will (A). (A) is determined entirely by (I) and (I) is determined entirely by external force (E). Does this truly bring about a different picture than if (E) had directly brought about (A)? In the scenario I just presented, the act of will is the same when it is directly brought about by (E) as when it is indirectly brought about by (E). Furthermore, since (I) was determined entirely by (E), there is nothing that (I) brought to the table that may even hint at changing the deterministic story.
Of course there will be cases where (E) influences (I) and (I) brings something new to the table before it brings about the act of will (A), but this does not always have to be the case. It seems that when it is not the case that (I) brings about its own new influence, that adding the extra link does not change anything in regard to the causal story. Yet, Descartes did not make any of these clarifications or differentiations. He was completely fine with saying that as long as there is an indirect relation between (E) and (A), (A) is not determined, and I have a real problem with saying that.