Teaser: Are we still defining free will in terms of acausality? Are we still defining morality in terms of objective truth?
As a student of philosophy (waaay back then) and an atheist, I was intrigued with the kind of concept God was. After only a little bit of work I learned that, as an explanatory device, God was a failure. For many, the idea that it explained everything was persuasive, but I saw that it prohibited nothing and realized that as an explanatory device it provided us with a goose-egg in terms of predictive power. I referred to it as a God-concept (go figure!), and started looking for others...
In analytic ethics, I came across the plethora of theories based on this idea of "self-interest." What was interesting about the idea of self-interest is that every possible choice could be characterized in terms of self-interest. It soon became plainly obvious that the reason for this was the way in which the concept was defined. It explained all possible behaviours, including self-contradictory ones, and prohibited none, and in so doing, negated any predictive power the idea had. I had found another God-Concept and this one was commonly accepted among contemporary scholars. Again, arguments from self-interest are ridiculously persuasive precisely because self-interest seems to explain everything.
In the meantime, altruism had been defined out of existence...
Along came determinism. For me it was in the form of Skinnerian behaviouralism. It's central effort was an attempt to turn psychology into a science by dealing only with what could be "verified" (external behaviour) and (pretty much) ignoring everything else. A passing nod was given to internal states by suggesting that our feelings of free will and the like were us experiencing our behaviour. It also assumed a causal (or at least correlational chain) between antecedent events and consequent behaviours. Again a scientific way of looking at things. At first I played along with it, trying determinism on for size as it were. It quickly dawned on me that it could explain every behaviour as a consequent of antecedent causal events including self-contradictory ones. Very persuasive. The next obvious task was to try to find a behaviour example it does not explain. Still looking - and this is where determinism gets interesting: Where is the falsifiability? That's right. Another God-concept.
So, to be perfectly honest, I dismiss determinism as an explanatory device for exactly the same reason I dismiss God and self-interest as explanatory devices: they have no predictive power because they "explain everything and preclude nothing." Now, I'm not saying that I don't think determinism has something to offer us, however, to assume it is the truth is as much an error from a scientific perspective (not even considering a skeptical perspective) as it is to accept God as an explanatory device. I suspect it is the first step down a long path, but it is not, as far as I can tell the end point.
Now, there can be any number of possible and different ideas about free will, not all of which need be supernatural in nature. The interesting thing, historically, is that religion sought to annex human volition (just as it sought to annex just about every other human quality and function) within its supernatural framework and most have come to accept this, including, I suspect, some folks critical of religion - perhaps to the point where they dismiss free will on the basis of its presumed supernatural association. Perhaps the reason we see free will as a supernatural breaking of a causal chain is because we rarely try to phrase it any other way, or perhaps more to the point, because determinism presents us with a dichotomous understanding of determined vs uncaused - a dichotomous relationship supported and promoted by religion seeking to present itself as the fundament of free will.
One such non-supernatural way of viewing free will might be as an emergent property of mind as a social construct. I am not saying this is the case, nor am I able at this point to defend it. All I am suggesting is that it may be possible to posit something functionally identical to (or very much like) free will in non-supernatural terms. Perhaps free will is something that naturally arises from our distinction between self and environment, or perhaps from some other aspect of our understanding of self. This is not as new-agey as it may sound. After all, if one conceives of oneself as being comprised of three warring selves in constant conflict, is it any surprise that one feels internally conflicted? If one perceives of oneself as being a being of sin, is it any surprise that one feels the need for forgiveness? You could build a business off of those...
The point really is that just because a particular idea (even something as seemingly irrefutable as determinism) suggests that something is true doesn't mean it is. Of all people, skeptics (scientific skeptics included) must understand this. We've seen through it with respect to the first God-concept....
It may be that we are wholly determined beings, but for the time being, I do not see sufficient cause to accept that we are without allowing for possible alternatives...
Definitions Bind Us; Definitions Can Free Us
There was a time when morality was defined entirely in terms of absolutist commandments imposed on us from some objective, independent of humanity, authority (namely: God). With such a definition, removing God from the equation meant decimating morality. Then we started defining morality as a social construct and matters started falling into place again. We labour under a definition of free will that entails acausality. With such a definition, free will is impossible. What if we started defining free will as a social construct...?
Perhaps in a very real sense, we are what we define ourselves as being.