Philosophical study of the nature and scope of logic. Examples of questions raised in the philosophy of logic are: "In virtue of what features of reality are the laws of logic true?"; "How do we know the truths of logic?"; and "Could the laws of logic ever be falsified by experience?" The subject matter of logic has been variously characterized as the laws of thought, "the rules of right reasoning," "the principles of valid argumentation," "the use of certain words called logical constants," and "truths based solely on the meanings of the terms they contain