Are the Laws of Logic Necessary or Contingent?

Abstract

The question of the title appears reasonable, and interesting. At first glance, it seems it could be answered either way. Here is an argument to show that the laws of logic are necessary. A law of logic is, by definition, topic-neutral. If the law of the excluded middle is true, it applies not only to tables and chairs, but to atoms and quarks and to every sort of stuff. Because of this topic-neutrality, the laws of logic hold of any world, whatever it is like. So the laws of logic are necessary. This is a persuasive argument. But the necessity of logic has not gone unquestioned. Descartes, for one, believed the laws of logic to be contingent.' God decided that there should be no true contradictions. But he chose freely; he could have instantiated a different law. Or we may appeal to Quinean holism. No tenet of our theory is sacred. Any law may be revised in the light of recalcitrant experience. Since everything is revisable, nothing-not even a logical law-is necessary. I do not know which of these positions is right; I do not know how the question of the title should be answered. But I feel that it is a good question. It is substantive, worthy of discussion. Unfortunately, given two assumptions about the nature of modality, the question has no interesting answer. The laws of logic are not contingent. If they have any modal status at all, they are necessary in a most trivial sense. It is unclear what moral should be drawn from this conclusion. Perhaps it sheds light on the nature of logic. Or perhaps my argument shows that the assumptions about modality need some rethinking. I say a little more about this in the last section of this paper.