Since the very beginnings of philosophy, the multifaceted problem of time has constituted one of the central concerns of philosophers and other thinkers. From pre-Socratic speculation to Platonic metaphysics, from St. Augustine to the medieval theologians, meditation upon time was unceasing, and the issue became yet more acute with the development of modern philosophy following Descartes (and t he subsequent emphasis o n the subject). One might summarize the slow evolution of Western thought in this area as follows: time began in Greek philosophy as a property of the world, was later referred basically to human beings, and in the twentieth century has recovered its cosmic nature thanks to contemporary physics ( notably the theory of relativity and its astrophysical and cosmological consequences). It is of course beyond the reach of a single article to tackle the problem of time in its entirety. Here, I shall concentrate on a single very specific aspect: the definition of the past and the question of whether the past has any explicative value. It is largely on the answer to this question that the possibility of maintaining the coherent identity of historyas a branch of knowledge depends.