So what are we left with by which to defend freedom from the taciturn determinist's powerful argument? First, we need to look at how the argument works.
Let us assume some moral agent, Q. We want to say that Q is free if Q can cause some action X in a way determined either solely or primarily due to Q, and if Q could have willed to act otherwise. Q is not its own cause; it cannot be. Nothing is the cause of itself. So, Q was caused by some cause or set of causes, which we will can label P. P caused Q; and now Q exists in some determinate way because of P, a way which makes P the sort of thing that would do X rather than not X. Now Q performs some action, X. It is certainly true that Q causes X, but because Q's nature is determined by P, it is also true that action X proceeds from a state of reality which Q did not create nor bears any responsibility for. It cannot, then, be the case that Q causing X is due primarily to Q's will; Q may genuinely will X, but Q genuinely wills X because P caused and determined Q to be such an such a thing that would do X rather than not X. Furthermore, because Q is such a thing that would do X rather than not X, it is also not the case that Q is really free to have acted otherwise.
I contend that the entirety of the argument rests on the notion of causal determination, or the idea that causation always determines the nature of the thing caused. Because P caused Q, P also determined Q with respect to all its properties, including whether it is the sort of thing that would do X rather than not X. Now, practically speaking, it seems like a no brainer to state that whatever causes a thing will also determine all of that thing's relevant qualities; for example, if one cue ball strikes another and causes it to go off in some direction, it also determines the direction that other ball will go. This is true universally, it seems, and in such a way that the argument above basically takes it for granted that P not only caused but also determined Q, and furthermore that this determination includes P's being the sort of thing that would do X rather than not X. But the entire point of free will is that causation does not always mean determination - that is, that some faculty called free will involved with Q choosing X is not determined by P, but is rather self-determined (which is something distinct from being self-caused). In other words, the argument sidesteps the traditional understanding of free will by positing that because P caused Q, it also determined that Q would do X. Because this is precisely what free will theory posits, namely, that P does not necessarily determine that Q will do X, there seems that free will has a line of response: putting forward a sensible theory explaining how a faculty can be self-determining.
Free will theory must assume (as it traditionally has) that the will is self-determining, which is different from it being its own cause. It is true that the will is not its own cause: like the rest of the human person, it is the product of a vast number of different causal factors. But even though these causes might provide limitations to the will (we cannot will literally whatever we want, which is something I will discuss later), I do not think it is necessary to say that these causes determine the will.
But how can this be, especially considering our common experience of determining causality? It may be helpful to note that my example of determining causation involves physical mechanics: one something bouncing off another. In a strictly materialist world, all interactions and entities whatsoever are ultimately reducible to similar events, in which there can be no intelligible doubt that causation also means determination. I think it is clear that a determinist will win the an argument as long as materialism is a unquestioned assumption. But I will not allow it to go unquestioned: why must we believe that all the relevant entities or qualities by which Q choose to do X are strictly material? There is a rich philosophical, not even to mention theological, intellectual history for the non-materiality of some aspects of the human person. For the rest of my argument, then, I will make a counter-assumption to materialism: Q possesses a faculty, namely, free will, which is incorporeal in nature.
In discussing the assumption that we have some incorporeal component to our nature, I would like to strongly resist what I believe are easy fallacies. First, I am not proposing that my "real" self is something incorporeal, and that my body is therefore merely a shell or empty framework in which the real me dwells and which is under my control. If someone were to kick my leg, they would be kicking me, not merely my apparent outer form. I also want to resist the idea that the will, or any aspect, needs to be "entirely incorporeal." These two ideas both present dualities, in which incorporeal and corporeal are separate or even opposed realities. Rather, I mean to say that I am a union of incorporeal and corporeal realities; one can effect the other, they are intertwined and even, to some degree, inseparable. At the very least, to attempt to talk of the "soul" or "mind" without reference to the body is to distort the human person.
From the idea that the will has an incorporeal nature I will make an argument that Q's free will is caused by P but not determined by P. I will discuss this argument further in the next part.