Brain sciences can show that our acts are caused by deterministic processes in our brain and that our acts are often influenced by unconscious brain processes, but these facts alone cannot deny free will. Brain sciences are important rather because they, along with other biological and behavioral sciences, offer the data that seem troublesome for compatibilists. The problem of free will cannot be solved either by conceptual analysis alone or by empirical research alone. Whether we endorse reductionism or non-reductionism, it is necessary to revise our commonsense concept of free will to establish compatibilism.