We will leave the question of whether chance exists objectively, or whether all events occur according to certain laws, to philosophers. However, subjectively, chance certainly exists. We consider that all events, whose occurrence does not follow from the properties of the system that is the subject of our interest and whose behaviour we wish to explain, are governed by chance. For example, the extinction of the dinosaurs at the end of the Mesosoic as a consequence of the impact of a cosmic body was a chance event from the standpoint of a biologist, as it was not possible to derive in any way that it would occur from the properties of the organisms that occurred at that time on the Earth and from the laws governing the development of living systems. Simultaneously, it is of no importance whether or not it was determined at the instant of formation of the solar system that this cosmic projectile would collide with the Earth and thus whether it was or was not possible to predict that this would occur from knowledge of the positions and movements of the bodies of the solar system (and its surroundings) and on the basis of the laws of physics.