ABSTRACT
Man is a part of Nature, not something contrasted with Nature. His thoughts and his bodily movements follow the same laws that describe the motions of stars and atoms. The physical world is large compared with Man-larger than it was thought to be in Dante’s time, but not so large as it seemed a hundred years ago. Both upward and downward, both in the large and in the small, science seems to be reaching limits. It is thought that the universe is of finite extent in space, and that light could travel round it in a few hundred millions of years. It is thought matter consists of electrons and protons, which are of finite size and of which there are only a finite number in the world. Probably their changes are not continuous, as used to be thought, but proceed by jerks, which are never smaller than a certain minimum jerk. The laws of these changes can apparently be summed up in a small number of very general principles, which determine the
past and the future of the world when any small section of its history is known.
