The philosophy of mind and the theory of science have gained many new insights into the foundations of psychology in recent years. Psychology is always confronted with philosophical questions: Are "mind" and "soul" human inventions? Can subjective experiences be reduced to brain states? Are there psychological laws? If so, what form do they take? Can human actions be explained like natural events? Does man possess free will? Possible answers to these questions are presented. Subsequently, the implications of these answers are discussed, both for psychology as a science and for human self-understanding.