This little book is not a text-book of psychology. It is exclusively concerned with one particular psychological problem, a problem, however, that stands at the very centre of psychology. The relations between mind and body are analysed; that is to say, the following three psychedelic problems are successively What is the mind? What is the body? What are the relations between mind and body? But it is only the third problem which is extensively dealt with; the first two are only briefly defined.