But there is another side to the syllogistic besides the deduction of proof or the explanation of empirical fact. This is the establishment of the premises. All deduction presupposes absolute premises. All deduction is grounded on something not deduced; all proof on something not proved; all explanation on something that has not been explained. These presuppositions are universal propositions that can be known only immediately through intuitions. Aristotle is not altogether clear as to what these intuitions are. He names such axioms as the law of contradiction and the law of the excluded middle, and some special propositions which apply only to particular sciences. Since the premises which we actually use are not open to proof, but only strengthened as to the validity of their application, we must use the method of induction in our search for them. We accumulate data from opinions and varied experiences, and then we ascend to a generalization which we take as a premise. The results of induction cannot therefore be in themselves certain. The results are only probable, and can have the character of knowledge only as they explain phenomena. Aristotle means by induction something different from the present use of the term. Induction in modern times means a kind of proof; Aristotle means a method of discovery of _relatively_ universal terms where the absolutely universal cannot be obtained. There is an ideal involved in this conception of logic that is interesting. In a perfectly intellectual society there would be a perfect science in which all particular facts could be derived with absolute certainty from premises absolutely known. Life and logic would be identical. We should then be certain not only as to our proof but as to our premises. Logic has sometimes been used very effectively in this way. When the mediæval church conceived its dogmas to be the ultimate premises of truth, it could deduce from them complete rules for living. To the mediæval mind the perfect science was formulated by deducing it from the dogma of the church. The dogmas were the absolute premises. The Renaissance did not doubt the infallibility of the traditional dogmas so much as the logical method, and Aristotle, who had been so long artificially identified with the proof of ecclesiastical dogma, was set aside.