Natural Philosophy is a science which, in its evident sense, includes all scientific knowledge which is based upon natural law. A mere record of phenomena, however interesting, would not be included in natural philosophy; but directly an explanation of these phenomena can be given, directly we can measure the effects of any given cause, then their study rises to the level of philosophy. It is usual to limit the term natural philosophy to that branch of science which deals with the behaviour of bodies when they do not undergo any change in themselves. Chemistry and botany are hence excluded, while astronomy, although really a branch of natural philosophy, has become so vast a subject that it, too, is excluded and left to form a separate science. Natural philosophy is thus limited to the various branches of physics (q.v.).