Tractatus versus Quantum Mechanics

This paper is divided in four parts. In the first part we introduce the method of internal critique of philosophical theories by examination of their external consistency with scientific theories. In the second part two metaphysical and one epistemological postulate of Wittgenstein's Tractatus are made explicit and formally expressed. In the third part we examine whether Tractarian metaphysical and epistemological postulates (the independence of simple states of affairs, the unique mode of their composition, possibility of complete empirical knowledge) are externally consistent with the theory of quantum mechanics. The result of the inquiry is negative: Tractarian postulates ought to be be revised. Relying on the result we approach the question of the empirical character of logic in the fourth part. The description of theoretical transformations of the notion of disjunction, in its ontological, epistemological, and logical sense, is a common element of in all parts of the text. The conjecture on the existence of different types of disjunctive connectives in the language of quantum mechanics concludes the paper.