The law of three stages and hierarchy of sciences are intimately related. The sciences also pass through similar stages in their development. The rate of development depends upon the proportion of its generality, simplicity and independence of the rest. Thus, Astronomy was the most simple and most general of all sciences as it developed first. It was followed by the development of physics, chemistry, biology, and finally, sociology. Each science in this order depends on its predecessors for its development as the hierarchy is marked by the law of increasing complexity and decreasing generality.
August Comte relates Sociology as closest to Biology. The reason for this is that just as biology studies the body parts in relation to the whole organism it also studies the social institutions in light of the whole social order. It differs from other sciences in the sense that unlike Physics, Chemistry and Astronomy it does not study its subject in abstractions as only inorganic elements are better understood that way.