The words ‘logic’ and ‘grammar’ are understood by all of us to refer to quite intricate doctrines, investigations, etc., which are presented in books which have been written in the past and which continue to be written in the present time.

Nach P. Janich wird eine "Uhr" definiert als ein Gerät, bei dem sich ein Punkt längs einer Geraden gleichförmig bewegt. Zur Definition von "gleichförmig" wird erst die "Ähnlichkeit" uhrenfrei definiert. Anschließend kann die "Eindeutigkeit" der Zeitmessung dadurch bewiesen werden, daß die Ähnlichkeit aller Uhren bewiesen wird. Die Gleichförmigkeit läßt sich jedoch, wie hier gezeigt werden soll, auch schon vor der Ähnlichkeit definieren.

"Logic", one of the central words in Western intellectual history, compre hends in its meaning such diverse things as the Aristotelian syllogistic, the scholastic art of disputation, the transcendental logic of the Kantian critique, the dialectical logic of Hegel, and the mathematical logic of the Principia Mathematica of Whitehead and Russell. The term "Formal Logic", following Kant is generally used to distinguish formal logical reasonings, precisely as formal, from the remaining universal truths based on reason. (Cf. SCHOLZ, 1931). A text-book (...) example of a formal-logical inference which from "Some men are philosophers" and "All philosophers are wise" concludes that "Some men are wise" is called formal, because the validity of this inference depends only on the form ofthe given sentences -in particular it does not depend on the truth or falsity of these sentences. (On the dependence of logic on natural language, English, for example, compare Section 1 and 8). The form of a sentence like "Some men are philosophers", is that which remains preserved when the given predicates, here "men" and "philosophers" are replaced by arbitrary ones. The form itself can thus be represented by replacing the given predicates by variables. Variables are signs devoid of meaning, which may serve merely to indicate the place where meaningful constants (here the predicates) are to be inserted. As variables we shall use - as did Aristotle - letters, say P, Q and R, as variables for predicates. (shrink)

This book is an attempt to relate the operative and constructive formulation of symbolic logic carried out by Lorenzen—and to a lesser degree Kolmogorov and Markov—to both Wittgenstein's philosophy of logic as set forth in the Tractatus and later modified in the Investigations, and to Brouwer's critique of classical logic, especially the principles of excluded middle. The first chapter contains an exposition of Wittgenstein's critical analysis of the "mythical" views of Russell and Frege; and it develops his own "operative" (...) theory of elementary logic. The second chapter concerns the relations of the theories of Brouwer and Wittgenstein; the last section is a detailed survey of chiefly Lorenzen's operative logic in which the presentation of a dialogue-like interpretation of logic is exhaustively analyzed: the notion of a "winning strategy" in such a two-person dialogue is set forth, the technique is extended to classical logic from its original, weaker operational form, and its relations to Gentzen's Sequenzen-kalkül is discussed. The work was the author's Habilitationsschrift at Innsbruck University.—P. J. M. (shrink)