ABSTRACT
The answers that we may give to these questions together constitute a philosophy of evolution, which is carefully to be distinguished from evolution as a scientific theory. As a scientific theory evolution is an account, as exact as science can make it, of what actually did happen in the past, of the precise process by which things have come to be what they are. When this knowledge has been gained, we may ask the question, What value has this knowledge for the practical purposes of life ? And the answer will be a contribution to philosophy, but it will not be one of the things described by science as having happened in the past, will not be part of the knowledge from which it is itself inferred, nor, if it is a false inference, will it have any right to masquerade as science and say that we must accept it as true or else deny the
truth of science. Indeed, we found that two answers to the question, two philosophies of evolution, the Optimistic and the Pessimistic, have been formulated, which being contradictory cannot both be true, though both may be false.
