Examining Wittgenstein's Tratatus Logico-Philosophicus in both German and English, the words "synthetic(al)" and "posteriori" do not appear when I searched for them. However, "a priori" often did. The word "analytical" was mentioned in 6.11. Wittgenstein mentioned Kant once regarding the problem of the left and right hand in 6.36111.
Wikipedia describes Kant's distinction between a priori and a posteriori as follows:
These terms are used with respect to reasoning (epistemology) to distinguish "necessary conclusions from first premises" (i.e., what must come before sense observation) from "conclusions based on sense observation" which must follow it. Thus, the two kinds of knowledge, justification, or argument, may be glossed:
- A priori knowledge or justification is independent of experience, as with mathematics (3 + 2 = 5), tautologies ("All bachelors are unmarried"), and deduction from pure reason (e.g., ontological proofs).[note 1]
- A posteriori knowledge or justification depends on experience or empirical evidence, as with most aspects of science and personal knowledge.
Furthermore, G. E. M. Anscombe quotes (page 25) Karl Popper (*British Philosophy in Mid-Century, Allen and Unwin, 1957: pp. 163-4) as writing
Wittgenstein tried to shew that all so-called philosophical or metaphysical propositions were in fact non-propositions or pseudo-propositions: that they were senseless or meaningless. All genuine (or meaningful) propositions were truth-functions of the elementary or atomic propositions which described "atomic facts", i.e. facts which can in principle be ascertained by observation.
She claims there is little discussion of such matters in the Tractatus: (page 26)
Someone who, having read the Tractatus, reads Popper's account of it, must be struck by one thing: namely that there is a great deal about 'observation' in Popper's account, and very little about it in the Tractatus.
This should give the reader pause. What the reader expects Wittgenstein to be saying because he is talking about propositions and logic may not be his message. Wittgenstein summarizes the book in the preface: (page 27)
The book deals with the problems of philosophy and shows, as I believe, that the method of formulating these problems rests on the misunderstanding of the logic of our language. Its whole meaning could be summed up somewhat as follows: What can be said at all can be said clearly; and whereof one cannot speak thereof one must be silent.
There is a possibility that Wittgenstein may not be interested in Kant's distinction between analytic and synthetic propositions. His interest was in the a priori, the "logic of our language" and not observation.
Anscombe, G. E. M. An Introduction to Wittgenstein's Tractatus. 1971. St. Augustine's Press.
Wikipedia contributors. (2019, April 4). A priori and a posteriori. In Wikipedia, The Free Encyclopedia. Retrieved 16:41, May 14, 2019, from https://en.wikipedia.org/w/index.php?title=A_priori_and_a_posteriori&oldid=890860331
Wittgenstein, L. Tractatus Logico-Philosophicus. 1922. Retrieved on May 14, 2019 from https://archive.org/details/in.ernet.dli.2015.221720/page/n29