For the first time in Russian literature, the book sets out in a fairly accessible form the theoretical foundations of biological systematics - a scientific discipline engaged in the development of the Natural System of Wildlife. The structure of systematics, its background and the history of its scientific revolutions are characterized. The philosophical foundations of systematic research, the structure and content of taxonomic theories, research programs in systematics are briefly considered. The scientific puzzles of taxonomy have been analyzed, the solution of which is occupied by theorists and practitioners.