We saw in the preceding chapters that from the time of Newton there has been a slow but systematically growing process of the penetration of the natural sciences into philosophy. At first, the process applied only to physics. Its appearance on the scientific scene of modern times was a fact so important that other fields of thought had to react to it. Later, the significance of other sciences, particularly biology, began to grow. Before long almost everyone who considered himself to be a philosopher felt the necessity of saying something either about the natural sciences directly or at least about the problems about which the natural sciences also spoke. For many of them, the achievements of the sciences became either an inspiration for their own reflections or a point of departure from which to elaborate philosophical generalizations