The book of the outstanding philosopher and logician of the 20th century Karl Raimund Popper “Objective Knowledge” was published in the first edition in 1972, the second - corrected and expanded, from which a Russian translation was made, in 1979. It occupies a special place among Popper’s works: it is - the third, after The Logic of Scientific Research (1934, 1959) and Conjectures and Refutations (1963), his classic work on philosophy, epistemology and the logic of science. It summarizes the results of Popper's previous studies of the problems of induction, falsificationism, critical rationalism, the plausibility of scientific theories, etc., and also sets out the results obtained at the time of its writing of his development of the theory of three worlds, the role of the concept of “truth” in the philosophy of science, problems of evolutionary epistemology and etc. The latter problems were the focus of Popper's attention until the end of his life. The Russian translation of this book contains the “Afterword to the Russian edition of Objective Knowledge,” written by one of Karl Popper’s students, co-authors and closest friends, David Miller.