The arguments which logicians worry about come in all shapes and sizes, from every corner of the intellectual globe, and are not confined to any one particular topic. The central problem which worries the logician is just this: how, in general, can we tell good arguments from bad arguments? Modern logicians have a solution to this problem which is incredibly successful and enormously impressive. For logical purposes, an argument simply consists of a sentence or a small set of sentences which lead up to, and might or might not justify, some other sentence. In logical terms the Blind Lemon Jefferson argument is a valid argument, i.e. quite simply, if the premises are true, then the conclusion must be true, on pain of contradiction. The Blind Lemon Jefferson example also illustrates the point that logic is not really concerned with particular matters of fact.