ABSTRACT
2.1. Mathematical Logic produced by four lines of thought. Mathematical Logic is the outcome of the joining together of four different lines of thought. These are the old logic, the invention of Aristotle; the idea of a complete and automatic language for reasoning; the new developments in algebra and geometry which took place after 1825; and the idea of the parts of mathematics as being systems of deductions, that is of chains of reasoning in agreement with rules of logic, these rules giving one the power to go from a statement s1 to another statement s2 when s2 is necessarily true if s1is is taken to be true. We will say something about these four in turn.
