Taking the universe as I find it, I find
a.) Some of my actions are free, and
b.) All of my actions arise from (at least one) antecedent agent.
I could pit the truth of (b) against (a) and deny free will out of some sense of determinism, or pit the truth of (a) against (b) and imagine that my free acts literally prove that I am God (through, for example, Thomas’s Second Way) but I’d rather just take the universe as it is and move on to the question of what sort of antecedent agent could be responsible for my own genuinely free action.
I’ll take it as given that if either you or some other mechanico-natural process sufficed to explain my doing an action, I should conclude my action wasn’t free, and that any judgment or feeling I had of doing the act freely would not be genuine, but illusory. So it looks like it doesn’t matter whether the antecedent cause is voluntary or mechanico-natural: either way I’m not free.
Taking a closer look, however, one notices the unspoken assumption that I consider antecedent causes only in a qualified sense, since I take something of the effect as given in being, apart from the antecedent cause. The picture I’m assuming is “given A, and some B for which A is not responsible, A proceeds to do C using B” Since this is the only way that either we or a natural-mechanical cause can be antecedent agents, we have to start by looking at antecedent agents in this way, but this takes “antecedent agent” secundum quid, or with a qualification. An antecedent agent cause simpliciter suffices to explain B simpliciter, meaning there is nothing about B, or at least nothing existent and actual about B, that fails to arise from the agency of A.*
Seen in this way, asserting the incompatibility of free choice and antecedent divine agency commits the fallacy of secundum quid and simpliciter. When one reduces my action to a previous agent secundum quid, he has to account for whatever reality such causes take for granted in the effects they act upon. When one reduces my action to an antecedent agent simpliciter, by contrast, there is no reality at all apart from an act already accomplished. Relative to divine agency in its full extension,** I don’t have to say that what feels like free will is actually illusory, or that my brain process tricks me, since there is neither a “what it feels like” or a brain process apart from such agency. Said another way, as soon as I take anything about my reality as given, the work of the antecedent cause simpliciter is already done. This is not true when the agent is a mechanico-natural process, which requires accounting for the being that such agents are not responsible for, and leads one to conclude that what appeared to be given as self-causality must in fact be an illusion, perhaps an illusion that conveyed a reproductive advantage or whatever. On this account, notice, reproductive advantage is thoroughly objective and real, entirely apart from the antecedent agent, and it is necessary for it to be so. I have to say something about the reality that an antecedent cause secundum quid does not explain, and “illusion conveying reproductive advantage” is the best anyone has been able to come up with, at least under the assumptions that
(i) my actions arise from antecedent agents and
(ii) the only such agents are mechanico-natural ones.***
My claim is that (ii) is the fallacy of secundum quid and simpliciter. In fact, immaterial agents transcend material ones, meaning that the mechanico-natural is only matter and object for my choice, and not agent; and that the manner in which my choice itself demands divine actualization is not in a way that requires explaining my own given reality as illusory, since whether I take my objective reality as self-caused or an illusion befitting reproductive fitness, God’s causality would already be accomplished, and just as necessary to explain either.
Again, recall that the thesis here is to take freedom and antecedent causality as given, and to figure out what sort of agent could do this. I am not trying to prove that if God exists, we are free. God would exist and cause us whether we were free or not. But I do think the converse follows from the above, and that the truth of (a) and (b) given at the outset demand a divine antecedent agent.
*Causality is priority in being, but insofar as A presupposes B as given, the two are simultaneous or equivalent in being. To include such equivalence in the account of causality is to add a qualification to the causality.
**Divine causality can be taken either as creative or as governing. As governing, it takes the natures it deals with as given, causing them to move in certain ways. Governance, however, obviously presupposes creation, and so when we consider the full ambit of divine causality, there can be, by definition, no created reality outside of it.
***If our minds were controlled by CIA brain-rays or aliens or any created thing at all, these would be relevantly the same thing, i.e. antecedent agents secundum quid, or antecedent agents that presuppose some reality in their effects that they are not responsible for, and which must be explained given the hypothesis that the antecedent cause causes an action.