The most common taxonomy of free will theories of free will hinges on the distinction between compatibilism and incompatibilism, which respectively assert and deny the compatibility of free will with causal determinism. This is a useful distinction, but it does not throw light on a fundamental aspect of the debate, regarding how the different views conceive of the role that philosophy and science should play in tackling with the free will issue. In this perspective, another taxonomy will be presented and three families of theories will be distinguished: scientific isolationism (“Free will is a business of science alone”), interactionism (“Both science and philosophy have to deal with the free will issue”), and philosophical isolationism (“Free will is a business of philosophy alone”). In conclusion, it will be argued that interactionism is the right approach.