The figure of Oswald Spengler (1880–1936) stands apart in the history of German and world thought. Spengler single-handedly tried to rethink the generally accepted views on the evolutionary development of mankind: he opposed the linear description of history as endless, unstoppable progress. Instead, he proposed the concept of cyclical development, according to which new cultures arise, experience a period of prosperity, and then go through stages of decline and death. Each such cycle lasts about a thousand years, each culture has distinctive features that determine the thinking and actions of people. The very title of the work contains the thesis that was substantiated in the book: at the turn of the 19th and 20th centuries, the culture of the Western world, according to Spengler, entered a period of decline. The first volume of the book was published in 1918, bringing the author great fame and causing heated discussions. This work had a significant influence on sociologists Arnold Joseph Toynbee, Pitirim Sorokin, José Ortega y Gasset. The publishing design is preserved in PDF A4 format.