Logic as an activity deals with the interplay or the dialectic, as one thinks, between the known and the unknown, form and content, or the formal and the intuitive. For this purpose it is useful to select from what is taken to be known a universal part which remains fixed throughout all particular instances of the interplay. The propositions in such a universal part make up the logical truths. There are alternative answers to the question: What is to be required (...) of the concepts and the propositions of this universal part? Different choices can be and have been made with regard to the kind and the degree of their universality, and the degree of precision and systematic character of their codification. These different choices lead to different conceptions of logic, such as those of William of Occam, Kant, Hegel, Frege, Brouwer, the early Wittgenstein, the later Wittgenstein, and Gödel. (shrink)