Philosophy finds itself 'between tradition and another beginning.' 1 For this reason it seems necessary to reconsider the foundations of traditional philosophy in the hope that out of these considerations new questions may arise which may lead to a new philosophical foundation. To this end neither the large manual nor the monograph is well suited. What is required, instead, is to take a few steps which lead our thoughts directly into the problems of a given, traditional, philosophical foun­ dation. In this sense the present work wishes to provide an 'introduction' into that philosophical foundation which, until Hegel, had a decisive influence upon traditional philosophy_ Consequently, it does not see its task in providing a survey of this whole complex of problems. Nor does it offer solutions to questions about difficult passages which have been the subject of two thousand years of Aristotelian scholarship_ Instead, it follows a definite path which might bring this Aristotelian science, the theory which seeks to determine being as being, on hei on, closer to the student of philosophy.