What is true of phenomena is also true of their laws. Each order of phenomena has its special laws over and above those which result from its relations with the less complicated and more general orders. The idea of a supreme law from which all the others would be deduced must therefore be forsaken. Even within the range of each fundamental science, it is doubtful how far the unity dreamt of could ever be attained. The number of irreducible laws is far more considerable than is imagined by a false appreciation of our mental powers and of scientific difficulties. For instance, in physics, how can optics and acoustics be reduced to one another? Physiological considerations, in default of other reasons, would be opposed to such a confusion of ideas.[50] Likewise in biology, how can the laws of animal life be reduced to those of lower organic life? and in sociology, the laws of human society, implying a course of history, to those of animal societies which do not do so? Instead, therefore, of conceiving _a priori_, the phenomena and the laws as capable of a “reduction” which is, in fact, impossible, the positive method requires the determination of the general characters of these phenomena and of these laws by observations. It first establishes the following: 1. _The more complex phenomena become, the more also our means of studying them increase in number._ It is a natural but an insufficient compensation. For the difficulty of establishing the science of phenomena grows much more quickly than the number and the power of our methodical processes. However, without this compensation, scarcely any fundamental science would ever reach the positive state. Thus, to the method of pure mathematics observation in astronomy comes to be added. Experimentation appears in physics, the art of nomenclatures in chemistry, the comparative method in biology, the historical method in social science. With this final science, the positive method is henceforth complete. 2. _The more complex phenomena become, the more modifiable they are._