The concept of self-generated action is controversial, despite extensive study of its neural basis. Why is this concept so troublesome? We analyse the concept of self-generated action as employed by and. There are two definitions of self-generated action; as operant action and as underdetermined action. The latter draws on subjective experience. Experiments on action awareness suggest that experience may not be a good guide for defining self-generated action. Nevertheless, we agree with Passingham and colleagues that self-generated actions exist distinct from (...) operant actions. But defining ‘self-generated’ by the degree of involvement of an endogenous process risks regress. We sketch an alternative account of self-generated action that tries to avoid these problems to make self-generated actions accessible to experimental science. (shrink)