About the book: 1999 / The main work of the remarkable Polish humanist scientist, microbiologist and philosopher L. Fleck is published for the first time in Russian. T. Kuhn, in the preface to his famous book “Structures of Scientific Revolutions,” referred to the works of L. Fleck along with the brilliant names of A. Koyré, J. Piaget, E. Metzger and others as theoretical sources of his own views on the nature of scientific knowledge and the role of history of science in the formation of epistemological models. However, these works have independent scientific significance and allow us to consider L. Fleck one of the founders of modern sociology of science and comparative epistemology. The book will be read with interest by philosophers, natural scientists, historians, and anyone interested in the history of science, the fate of scientists and their ideas. This publication was published as part of the Translation Project program of the Central European University with the support of the Center for the Development of Publishing Activities (OSI - Budapest) and the Open Society Institute. Assistance Fund" (OSIAF - Moscow).