Discussions concerning the relation between science and philosophy are still likely to be carried on in terms of the controversy as to whether all knowledge springs from (or has its source in) experience. Yet it is becoming more and more apparent that the solution of this controversy will depend not on any fact finding but on a thorough analysis of the meaning of the terms “knowledge” and “experience.” Furthermore, it is generally admitted that the definition of these terms should not be arbitrary but in line with their usage among scientists.