Blackwell Reference Online

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P. F. Strawson once characterized logic as ‘the general theory of the proposition’ (Strawson 1967: 1). At this level of abstraction we can do no better. But what is a proposition? And what is such a theory? An initial answer might be: A proposition is the sort of thing that is true or false. Logic deals primarily with certain relations that hold between propositions, namely those which depend on which combinations of truth and falsity are possible. These relations are called logical relations. Two which are of central concern are consistency and consequence. A proposition is consistent with others when it is possible for them all collectively to be true. (The truth of the others allows for the truth of it.) A proposition is a consequence of others when it is not possible for all of the others to be true yet it to be false. (The truth of the others demands the truth of it: if they are all true, then it must be true too.) Consequence is the relation that holds between the premises and the conclusion of a valid argument. Each part of this answer requires clarification. In particular, attention settles on the three key terms ‘true’, ‘false’ and ‘possible’. The interesting thing is that, because logic also has a philosophical component, the very process of providing such clarification is itself part of logic. More precisely, it is part of philosophical logic. Logic subdivides into two: ... log in or subscribe to read full text