In Aristotelian physics, natural objects are characterized by their teleology, i.e. their tending toward certain ends. According to St. Thomas, what makes an event a voluntary action is that the subject of the event has knowledge of the end toward which the action is directed.
Post-Galileo, physics is not about teleology in this way. Instead, physics is about laws, rules according to which events unfold. Accordingly, many early modern philosophers hold that a voluntary action is an event which unfolds according to a rule which has been adopted by the subject of the event. The clearest statement of this idea I know of is at the beginning of section 3 of Kant’s Groundwork, but I think it can be found as well in Samuel Clarke and Thomas Reid, and maybe also Leibniz. I think it might also be implicit in Berkeley, which is why I’ve been thinking about it. So there’s a shift from regarding a voluntary action as one pursuant to an end adopted by the agent, to regarding a voluntary action as one pursuant to a rule adopted by the agent. Of course, for anyone who believes in free will of any robust sort (even a compatibilism of Leibniz’s sort), teleology can’t drop out entirely, the way it does for Spinoza, but rules of action acquire a new importance, and in many cases they seem to become more important than ends. For Reid and Kant, at least, this is also connected to deontologism in ethics.*
Interestingly, for many early modern philosophers, the connection between rules and voluntary action goes the other direction as well. The view that the notion of a rule or law only makes sense if there is someone who prescribes the rule, either to himself or to some other agent capable of following it voluntarily, is behind a key argument for occasionalism with respect to the movements of bodies in Malebranche, Clarke, Berkeley, and Reid.
In the title of this post, I said I was going to give a hypothesis. I’m pretty confident about the basic facts here (though the statement of them is a little rough; this is, after all, only a blog post). The hypothesis is the explanatory connection between the facts: i.e. the claim that it was due to the shift in thinking in physics that the shift in thinking in action theory occurred. True or false?
* Reid emphasizes virtue a lot more than most deontologists, but for Reid a virtue is by definition a character trait formed by the conscious and intentional adoption of a rule of conduct (I defend this view in sect. 2 of “Thomas Reid on Character and Freedom”), so the rules are prior to either virtues or ends, which makes Reid, at least on some definitions, a deontologist.
(Cross-posted at blog.kennypearce.net)