In my dissertation I defend the thesis that rational intuition, as a source of a priori justification, should be given an important place within the epistemology and philosophy in general, and that they have not been adequately explained within the framework of rationalists’ and empiricists’ theories. Consequently, most of the work I dedicate to the presentation of their theories and emphasizing the main problems they are dealing with. Empiricists’ theories, whether they are moderate or radical version of empiricism in question, by renouncing intuitions their status of the source of a priori justification, lose plausibility of their explanations of how certain propositions are known independently of experience. Rationalists’ theories, on the other hand, by using primarily a priori methods of “armchair thinking”, fail to adequately explain what intuitions are, how they function, and to answer the question why we should consider them as a source of a priori knowledge, that is, why we should consider them as those that are truth conducive. So, the main problem in modern epistemology is the fact that evidential (justificational) status of intuitions, as a source of a priori justification, and method to which the philosophers in their argumentation appeal, is never fully explained.