This conclusion is used in the writings of both Comte and Mach as a kind of Occam's Razor for defining similar special objectives so far as the improvement of actual science is concerned. For example, both men are, on the strength of it, opposed to any attempts to deduce natural laws from special properties attributed to physical reality and both men feel that the concept of reality itself in the sense of something of which the laws are functions is superfluous. On the other hand, the premisses of the principle expressed in this conclusion have remained the fundamental consideration for positivism, since positivism has based itself upon them both to explain and to justify deviations from the principle in historical science. Thus, in Comte, the fact that the history of science is filled with
attempts to explain laws is justified as well as explained in terms of a natural development which it is supposed human thinking had to undergo in regard to the idea of causality. This development roughly involved three stages according to Comte: a theological stage, during which it was natural for human beings to refer natural effects to invisible divine agents or forces; a metaphysical stage, during which the old divine agents and forces were made a part of nature itself but nevertheless retained a theological element in that they were still invisible and were still imagined to produce phenomena; and finally the positive or positivist stage, in which we are at present, and during which the metaphysical concept of causality is being gradually replaced by the concept of causality in the sense of observed regular succession or connection, i.e., law. Moreover, according to Comte, this development is unequal in the various sciences, and not complete in any of them, so that it ought not to surprise us that a science like biology, in which metaphysical elements still prevail, lags behind a science like physics which has more nearly abolished them.