I've been thinking lately about the story of the donkey and the two stacks of
The donkey in question is usually referred to as 'Buridan's ass' (although there is some question as to whether the example is properly attributed to the medieval philosopher John Buridan .)
The early modern philosopher G. W. Leibniz was quite fond of this example, and appealed to Buridan's ass in order to elucidate his view that there was no such thing as a completely indifferent decision, that is, a decision made on the basis of no reason whatsoever. According to Leibniz, if the ass were in the hypothesized position and were indeed indifferent to the two piles of hay, then the ass would not be able to decide between them, and would consequently starve. Of course, the ass doesn't starve. Leibniz drew the conclusion that the reason that the ass wouldn't starve was because the ass wasn't actually indifferent to the bales of hay: according to Leibniz, there must be some difference between the two bales of hay, or in the ass's relation to the bales of hay--that is, some difference in the ass's perception of the bales of hay, even if only a difference in the representation of the bales of hay that is not consciously accessible to the ass--that would explain why the ass chooses one bale of hay rather than the other (and hence is able to choose one and not starve).
Leibniz deployed this example not out of any special concern for animals, but because he was opposing the view, widely held in the late medieval and early modern period, that freedom consisted in the ability to act or not to act. Leibniz thought that this view made no sense: for one thing, it flouted the principle of sufficient reason, according to which every natural event had to be explicable, and it seemed to him that a choice undertaken in a state of indifference was inexplicable. While this principle has considerable intuitive appeal, not all philosophers share Leibniz's intuition--indeed, certain late medieval philosophers, and certain recent philosophers as well, who share the late medievals' intuitions--would have denied Leibniz's assumption that an agent's choice must be explicable in terms of reasons independent of the agent's capacity for choice itself.
We now come to the heart of the issue: do agents have the capacity to determine themselves, or all events in nature, including free choices, determined by antecedent reasons or causes? This is the deep question underlying the example of Buridan's ass; consideration of this question takes one to the heart of the problem of free will. Does the capacity for freedom require that agents be able to determine themselves, as 'libertarians' hold? Or can an agent be free even if her choices are determined by reasons or causes that are outside of her control, as 'compatibilists' hold? We thereby see how much hay can be made out of a seemingly footling and trivial example.