Aristotle distinguished between mere sense knowledge (sense-data) and abstract knowledge which generates concepts or ideas. Ideas in turn are combined to form judgments or propositions. Propositions are linked together to form chains of reasoning. From given or known premises we arrive at conclusions this process is called deductive reasoning, and one type of deductive reasoning is called syllogistic inferences or simply syllogisms. A fact is a true statement or proposition; a physical or observable fact is a true statement or proposition about observable things. According to Aristotle, it is one thing to know the facts and quite another to know the reasoned facts; it is the second that produces philosophic knowledge. Indeed, philosophy, for Aristotle, is reasoned or proven knowledge. When we examine the philosophic works of the other Greeks this definition seems to bear him out for the Greeks were interested not merely in knowledge but in proven knowledge. The premises are the cause of the conclusion; we know the conclusion by means of its causes-the premises; it is in this sense that philosophy is said to be knowledge by means of causes, otherwise we would never be capable of philosophic knowledge about God, for God has no causes.