The philosophical thought of the twentieth century is now becoming an object of historical analysis. But its reconstruction presents many difficulties, and the attempts at a general view are hitherto largely unsatisfactory. The paper aims to single out the main variables to be considered in order to give a picture of the contemporary philosophy: 1) the existence of different national traditions; 2) the formation of philosophical tendencies (and schools), some related to the past and some of more recent origin; 3) the development of "special" philosophical disciplines. A further crucial element for the understanding of the philosophical thought of the twentieth century are its relationships with scientific development, with religion, with politics. The paper ends with a reference to the problems of the periodizing of twentieth-century philosophy.