The aim and method of the strict type of naturalism may be easily defined. In its details it will become more distinct as we proceed with our analysis. Taking it as a whole, we may say that it is an endeavour on a large scale after consistent simplification and gradual reduction to lower and lower terms. Since it aims at explaining and understanding everything according to the axiom principia non temere esse multiplicanda [principles are not to be heedlessly multiplied], explaining, that is, with the fewest, simplest, and most obvious principles possible, it is incumbent upon it to attempt to refer all phenomena to a single, uniform mode of occurrence, which admits of nothing outside of or beyond itself, and which regulates itself according to its own system of fundamentally similar causal sequences. It is further incumbent upon it to trace back this universal [pg 031] mode of occurrence to the simplest and clearest form possible, and its uniformities to the fewest and most intelligible laws, that is, ultimately, to laws which can be determined by calculation and summed up in formulÆ. This tracing back is equivalent to an elimination of all incommensurable causes, of all “final causes,” that is, of ultimate causes and “purposes” which, in an unaccountable manner, work into the network of proximate causes and control them, and by thus interrupting their connectedness, make it difficult to come to a clear understanding of the “Why?” of things. And this elimination is again a “reduction to simpler terms,” for it replaces the “teleological” consideration of purposes, by a purely scientific consideration of causes, which inquires only into the actual conditions antecedent to certain sequences.

But Being and Becoming include two great realms: that of “Nature” and that of “Mind,” i.e. consciousness and the processes of consciousness. And two apparently fundamentally different branches of knowledge relate to these: the natural sciences, and the mental sciences. If a unified and “natural” explanation is really possible, the beginning and end of all this “reducing to simpler terms” must be to bridge over the gulf between these; but this, in the sense of naturalism, necessarily means that the mental sciences must in some way be reduced to terms of natural science, and that the phenomena, processes, sequences, and laws of consciousness must likewise be made “commensurable” with and [pg 032] be linked on to the apparently simpler and clearer knowledge of “Nature,” and, if possible, be subordinated to its phenomena and laws, if not indeed derived from them. As it is impossible to regard consciousness itself as corporeal, or as a process of movement, naturalism must at least attempt to show that the phenomena of consciousness are attendant and consequent on corporeal phenomena, and that, though they themselves never become corporeal, they are strictly regulated by the laws of the corporeal and physical, and can be calculated upon and studied in the same way.

But even the domain of the natural itself, as we know it, is by no means simple and capable of a unified interpretation. Nature, especially in the realm of organic life, the animal and plant world, appears to be filled with marvels of purposefulness, with riddles of development and differentiation, in short with all the mysteries of life. Here most of all it is necessary to “reduce” the “teleological view” to terms of the purely causal, and to prove that all the results, even the evolution of the forms of life, up to their highest expressions and in the minutest details of their marvellous adaptations, came “of themselves,” that is to say, are quite intelligible as the results of clearly traceable causes. It is necessary to reduce the physiological and developmental, and all the other processes of life, to terms of physical and chemical processes, and thus to reduce the living to the not living, and to derive the organic from the forces and substances of inanimate nature.