The substance of this article revolves around Kenny's rhetorical question. It is a widely held view among lawyers and legal philosophers that the idea of criminal justice involves the presupposition of the freedom of the will, but there are good grounds for accepting some version of determinism as a working hypothesis to explain criminal behaviour. Judges themselves on occasion do this. Unless it can be shown, therefore, that determinism is either compatible with free will, or is itself an incoherent doctrine, the whole rationale of the criminal law as a form of social control stands exposed to criticism.