The book contains works written by one of the largest Russian experts in the theory of knowledge and philosophy of science - Sergei Vladimirovich Illarionov (1938-2000). Its main part consists of lectures on the theory of knowledge and philosophy of science, which were given for several years to graduate students of the Moscow Institute of Physics and Technology. The second section of the book contains the most interesting articles by S. V. Illarionov, devoted to the most important problems of the philosophy of science. The appendix includes poems by this richly gifted man and a recent interview with him. The book is addressed to specialists in the field of theory of knowledge and philosophy of science, graduate students and undergraduates.