In the following pages we shall confine ourselves entirely to this type, and we shall not laboriously disentangle it from the bewildering medley of ideas foreign to it, or attempt to make it consistent; we shall neglect these, and have regard solely to its clear fundamental principles and aims. Thus regarded, its horizons are perfectly well-defined. It is startling in its absolute poverty of ideal content, warmth, and charm, but impressive and grand in the perseverance and tenacity with which it adheres to one main point of view throughout. In reality, it is aggressive to nothing, but cold and indifferent to everything, and for this very reason is more dangerous than all the excited protests and verdicts of the enthusiastic type of naturalism, which it is impossible to attack, because of its lack of definite principles, and which, in the pathetic stress it lays on worshipping nature, lives only by what it has previously borrowed from the religious conceptions of the world.
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 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.