1. See Tlp 5.15–5.156. Wittgenstein deals exclusively with relative or conditional probabilities. However, since absolute probabilities are but relative ones relativized to an arbitrary logical truth, his remarks can be-and have frequently been—reworded so as to suit absolute probabilities. Wittgenstein does not indicate, nor do we know, whether his account of probabilities is original with him.
2. See Logical Foundations of Probability (Chicago 1950), §55—§58.
3. See “A Set of Independent Axioms for Probability,” Mind Vol. 47 (1938), pp. 275–277 (errata on p. 415 and p. 552 of the same volume). A corrected version of the paper is contained in “Two Autonomous Axiom Systems for the Calculus of Probabilities,” The British Journal for the Philosophy of Science Vol. 6 (1955), pp. 51–57 (errata on p. 176 and p. 351 of the same volume), and in Appendix *ii of The Logic of Scientific Discovery (New York 1959). Popper’s account of probabilities is original with him.
4. For a survey of probabilistic semantics see Leblanc’s “Alternatives to Standard First-Order Semantics,” in D. Gabbay and F. Guenthner (eds.), Handbook of Philosophical Logic, Volume I (Dordrecht 1983), p. 225ff.
5. See “Logic, Meaning, and Conceptual Role,” The Journal of Philosophy Vol. 74 (1977), pp. 379–409.