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application of formal logical techniques to philosophical problems

Logic As A Discipline
Nature and varieties of logic
It is relatively easy to discern some order in the above embarrassment of explanations. Some of the characterizations are in fact closely related to each other. When logic is said, for instance, to be the study of the laws of thought, these laws cannot be the empirical (or observable) regularities of actual human thinking as studied in psychology; they must be laws of correct reasoning, which are independent of the psychological idiosyncrasies of the thinker. Moreover, there is a parallelism between correct thinking and valid argumentation: valid argumentation may be thought of as an expression of correct thinking, and the latter as an internalization of the former. In the sense of this parallelism, laws of correct thought will match those of correct argumentation. The characteristic mark of the latter is, in turn, that they do not depend on any particular matters of fact. Whenever an argument that takes a reasoner from p to q is valid, it must hold independently of what he happens to know or believe about the subject matter of p and q. The only other source of the certainty of the connection between p and q, however, is presumably constituted by the meanings of the terms that the propositions p and q contain. These very same meanings will then also make the sentence “If p, then q” true irrespective of all contingent matters of fact. More generally, one can validly argue from p to q if and only if the implication “If p, then q” is logically true—i.e., true in virtue of the meanings of words occurring in p and q, independently of any matter of fact.