  There was no official philosophy of logic and mathematics in the LWS. Most Polish logicians treated logical studies as independent of philosophical commitments. Only Leśniewski had explicit philosophical views which influenced the form of his systems. This does not mean that concrete works were not influenced by philosophical ideas. Łukasiewicz’s many-valued logic and Tarski’s theory of truth are perhaps model cases. The former had the problem of determinism as its background and the second was strongly inspired by the Aristotelian tradition in thinking about truth. It was also the case that Polish logicians had inclinations to empiricism as a general epistemological attitude and this philosophy often resulted in sympathies to nominalism (Tarski), constructivism (Mostowski) and scepticism concerning the sharp distinction between logical and extralogical truth (Tarski). However, the technical side of logical problems decided about investigations and sometimes forced changes in philosophical standpoints. The example of Łukasiewicz is instructive once again. Although he at first thought of logic as a true or false description of reality, he later adopted a more conventionalist and instrumentalistic standpoint. This attitude allowed him to accommodate various ideas coming from rival foundational directions, that is, logicism, formalism and intuitionism. In fact, Leśniewski and Tarski contributed to the theory of logical types and combined it with the theory of syntactic categories; Tarski’s version in his work on truth is particularly important. Tarski also showed new perspectives for logicism by defining logical concepts as invariants under one-to-one transformations. He also contributed to general metamathematics (the theory of consequence operation) and intuitionistic logic. However, a very special feature of logical investigations performed in the LWS consisted in the free admission of all fruitful mathematical methods, including non-constructive ones. This was the main point of the set theoretical approach to the foundations of mathematics which replaced logicism.