In the free will debate, alternative possibilities, i.e. possibilities that one could have done otherwise than what she actually did, have been regarded as a necessary condition of our free will and moral responsibility. Now, are alternative possibilities compatible with determinism? A natural response might be ‘No’. However, the answer to this question rests on the interpretation of the modal claim ‘could have’ in the statement of alternative possibilities. Through this presentation, I will attempt to show a better interpretation of alternative possibilities which enables us to regard them as being compatible with determinism.

In explicating alternative possibilities from a point view of compatibilism, I will first consider ‘Classical Compatibilism’ and then proceeded to examine ‘New Dispositionalism’. The insight both views share is that alternative possibilities should be construed as a kind of agents’ abilities; so construed, alternative possibilities could be compatible with determinism. According to these theories, the claim ‘one could have done otherwise’ is equivalent to the claim ‘one had the ability to do otherwise’. Here, retaining abilities is obviously compatible with determinism. Though I think this argument is basically on the right track, it has several problems which need to be resolved. I will overview these problems and solutions next.

Classical compatibilism explains agents’ abilities by ‘conditional analysis’. However, conditional analysis has two fatal limitations. First, it fails to explain the ability to choose and the ability to try. Second, there are counterexamples against both the necessary and sufficient condition of conditional analysis. In order to overcome these defects, New Dispositionalism attempts to articulate the notion of abilities in terms of dispositions that has been much discussed in modern metaphysics for a few decades. Though this theory made an important progress in analysing the notion of ability, a fundamental difficulty remains. The difficulty is, simply put, that mere retaining of abilities is quite insufficient to ground our free will and moral responsibility. I hope this presentation considered a solution to this problem and showed a possible sophistication of the theory of alternative possibilities.

(Shohei Takasaki)