Aristotle

“ Those sciences are one and the same which belong to the same genus, namely those which have the same primary principles and common parts or essential qualities. One science differs from another when their elementary principles are not drawn from the same source, and when the principles of one science are not derived from those of the other. A proof of this may be seen when one reaches the indemonstrable propositions of a science. These, if the sciences be one, must belong to the same genus as the things which are demonstrated. ”