The book is not only dedicated to linguists, but also to readers who are not familiar with notations developed in linguistics. The first part of the study presents philosophical justifications for linguistic settlements. These are based on the phenomenological reduction of Edmund Husserl, Karl R. Popper's falsificationism, the moderate rationalism of science of Izydora Dambska and Andrzej Boguslawski's lack of the nomological explanation in linguistics. The second part presents a re-examination of the solutions proposed in the field of linguistics, some new philosophical explanations and a discussion of the truth of linguistic propositions.