The book of the famous American historian offered to the attention of readers is the result of the author's study of the works, peculiarities of thinking and circumstances of K. Marx's life between 1837 and 1846. Megill formulates his hypothesis about the "rationalistic" essence of the Marx project, expressed in his acceptance of the thesis of rationality built into the world, and reveals the criteria for this rationality (universality, necessity, dialectics, prognostics).