Abstract

I. Formal logic and metaphysics are not the same. Metaphysics asserts certain propositions [chu-chang] about things; formal logic differs in that it does not assert any proposition about any specific thing. It is precisely because formal logic asserts no propositions about things that it can serve metaphysics. For example, according to metaphysics, "All men die." Since formal logic asserts nothing about this, it can deduce a valid syllogism based on it, such as: "All men die; Chang San is a man; therefore, Chang San must die." Or again, according to metaphysics: "Metals cannot be melted." Of course this is false. But formal logic can deduce a valid syllogism even from this, such as: "Metals cannot be melted. Gold is a metal; therefore, gold cannot be melted." This is a case of formal logic serving an incorrect proposition. There are true propositions and there are false ones. The syllogisms based on propositions may in themselves be valid; but in order to determine the truth of a proposition, one must see whether or not it corresponds with reality. For example, if the proposition "metals cannot be melted" corresponds with reality, then it is considered true; otherwise it is false. To determine whether a syllogism is valid or not, one need only see if it itself is contradictory or not. For example, the above two syllogisms, in themselves, are not contradictory: "Chang San will die" and "all men die" are not contradictory. "Gold cannot be melted" and "metals cannot be melted" are not contradictory. Therefore, these two syllogisms in themselves are valid. There are true and false propositions, but syllogisms only need to be valid; they cannot be invalid. If formal logic were to serve only true propositions and be unable to serve false propositions, then it would have parted company with metaphysics long ago. But this is not the case, for it is clear that it can serve false propositions