Comte's second bestknown theory, that of the hierarchy of the sciences, is intimatelyconnected with the Law of Three Stages. Just as mankind progresses onlythrough determinant stages, each successive stage building on theaccomplishments of its predecessors, so scientific knowledge passesthrough similar stages of development. But different sciences progressat different rates. "Any kind of knowledge reaches the positive stageearly in proportion to its generality, simplicity, and independence ofother departments." Hence astronomy, the most general and simple of allnatural sciences, develops first. In time, it is followed by physics,chemistry, biology, and finally, sociology. Each science in this seriesdepends for its emergence on the prior developments of its predecessorsin a hierarchy marked by the law of increasing complexity and decreasinggenerality.
The social sciences, the most complex and the mostdependent for their emergence on the development of all the others, arethe "highest" in the hierarchy. "Social science offers the attributesof a completion of the positive method. All the others . . . arepreparatory to it. Here alone can the general sense of natural law bedecisively developed, by eliminating forever arbitrary wills andchimerical entities, in the most difficult case of all." Social science"enjoys all the resources of the anterior sciences" but, in addition, ituses the historical method which "investigates, not by comparison, butby gradual filiation." "The chief phenomenon in sociology . . . thatis, the gradual and continuous influence of generations upon eachother--would be disguised or unnoticed, for want of the necessarykey--historical analysis."
Although sociology has specialmethodological characteristics that distinguish it from its predecessorsin the hierarchy, it is also dependent upon them. It is especiallydependent on biology, the science that stands nearest to it in thehierarchy. What distinguishes biology from all the other naturalsciences is its holistic character. Unlike physics and chemistry, whichproceed by isolating elements, biology proceeds from the study oforganic wholes. And it is this emphasis on organic or organismic unitythat sociology has in common with biology. "There ca be no scientificstudy of society either in its conditions or its movements, if it isseparated into portions, and its divisions in its conditions or itsmovements, if it is separated into portions, and its divisions arestudied apart." The only proper approach in sociology consists in"viewing each element in the light of the whole system. . . . In theinorganic sciences, the elements are much better known to us than thewhole which they constitute: so that in that case we must proceed fromthe simple to the compound. But the reverse method is necessary in thestudy of Man and Society; Man and Society as a whole being better knownto us, and more accessible subjects of study, than the parts whichconstitute them."
From Coser, 1977:9.