The most detailed presentation of questions relating to all the most important branches of natural science and mathematics is given in Engels's work, Dialectics of Nature, which Engels worked on closely with Marx, which remains unfinished, but remarkable in its wealth of thoughts. Engels already in 1873 decided to write a large work on dialectics in nature. In a letter to Marx dated May 30, 1873, Engels shares with him his thoughts on natural science. Here he already formulates the three central ideas of his "Dialectics of Nature": 1) the continuity of matter and motion (motion as a form of being matter); 2) qualitatively different forms of movement and various sciences studying them (mechanics - physics - chemistry - biology); 3) dialectical transition from one form of movement to another and, accordingly, from one science to another.