There is a class of book, at present much in vogue, so much so as to afford a fair indication of what most strongly appeals to the average man, wherein are to be found pleasing descriptions of nature in garden, field, and hedgerow, at the pond side, by the seashore, in woodland glade, or on the undulating moorland tract watered by mists and copious dews. Delicate word-pictures and artistic illustrators conjure up before our eyes the chestnut in its glory of summer bloom, the autumn tints of beech and elm, the meadows golden with buttercups, the orchard laden with ripening fruit, the blackbird pouring forth his full rich notes, the little brown wren slipping in and out among the hedge sprays, the hovering kestrel or the soaring lark, the badger in his lair, the water-vole beneath the stream's overhanging bank, the dragon-fly darting over the rushes, the whirligig beetles in their mazy dance, the murmur of innumerable bees, and all the varied life of the countryside. One of their leading aims is to help us to see what we should otherwise pass unnoticed, to stimulate our interest, and, if it may be, to charm us by the fidelity of their reproduction of scenes associated with hours of relaxation. But they also skilfully utilise some of the facts and theories established by science. Geology, botany, zoology are laid under contribution; even physics and chemistry are administered in small doses. But for the most part only such admixture of science is tolerated as shall serve to heighten the general effect, or, to put it in another way, the science is subsidiary and contributory to an interpretation which is not meant to be primarily scientific Furthermore, a subdued note of purpose is generally present and is welcomed by the average man. Indeed, it is scarcely too much to say that for him it is the evidence of design in natural events which bestows on nature-study its central interest and its abiding value. These works serve therefore to exemplify what I have spoken of as the threefold appeal to the plain man.
For him, too, and for the modes of thought and expression which he represents, nature-study and natural science do not include the works of man, still less his mental attributes and his intellectual faculties. The distinction between natural and human products is accepted as an obvious and satisfactory basis of classification. Hence arises an imperium in imperio, a world of art in the midst of the world of nature. I am not sure that the average man thinks out very clearly the relations of the two empires; partly because the distinction is to him so familiar and obvious as to render it scarcely worth while to delimit the territories in any formal manner. He may not find it easy in all cases to say where and how and to what extent human purpose is impressed upon the natural world; but just in so far as that purpose does modify things and events have we the products of human art or artifice.
Such I conceive to be the outlook of the plain man in approaching the interpretation of nature. Different in two cardinal respects is the outlook of those who accept the teachings of modern naturalism. In the first place, man is regarded as a product of natural evolution a highly specialised product no doubt, but still, body and mind, of natural origin. It is, they will say, sometimes convenient to regard natural products and human or artificial products as belonging to different categories. But it is none the less incontestable that for scientific treatment this is exceedingly inconvenient. Just in so far as man does modify things and events, is he thereby shown to be part of the conditions and circumstances under which such modification occurs. And though it may be obviously convenient to distinguish the links on the one side from those on the other side of this, to us, the central human link, still from a broad and comprehensive point of view we should seek to include all the causal relations of the chain as a whole.
The supernatural interpretation of mental and spiritual phenomena, the exponent of naturalism will urge, is a relic of the days before psychology was recognised as a science working hand in hand with physiology. It is true that psychology is not commonly placed in the category of the natural sciences, and that no one could claim for it a place among the physical sciences. It is true that the chemist, the astronomer, the geologist, in their several contributions to the interpretation of nature, wisely take for granted the conscious and intellectual operations by which their results are reached. They assume, and they are quite right in assuming, a frankly objective standpoint. They extract from data somehow presented to the mind the laws of phenomena somehow elaborated by the mind. How presented and how elaborated it is not their special province to determine. But from a broad and catholic point of view we should not restrict the interpretation of nature to the contributions of any particular science, nor to those of any limited group of sciences. The real questions are these: Are the phenomena of consciousness itself closely and intimately related to the phenomena, such as physical events, which are presented in or to consciousness? Are mental products and processes subject to complete interpretation in terms of antecedence and sequence, or in other words are they open to scientific investigation? Granting that an affirmative answer is given, as naturalism asserts that it must be given, to these two questions, are there valid reasons for excluding the phenomena of consciousness from the category of natural occurrences? Naturalism is fully convinced that there are no such reasons; and its logical exponent is bound to urge that our conception of nature should be so far extended as to include those phenomena of consciousness, of which we see or infer the beginnings in the lower animals and the present culmination in mankind. Man is thus part of that nature which we endeavour to interpret on the basis of scientific study. As this is one of the contentions with which we shall be concerned, it may be well to distinguish two forms which it may assume: (1) Man forms part of the naturalistic universe of discourse; (2) within that universe is to be found a complete interpretation of all human aspiration and endeavour.
In the second place, naturalism is at variance with popular thought in its attitude towards purpose. This is regarded as a product of evolution; whereas the average man regards it as that which directs the evolutionary process. The contention is that there is sufficient evidence of purpose in the sphere of human life and endeavour, and that its natural genesis has to be explained; but of purpose in the realm of nature, beyond the sphere of human influence, there is not sufficient evidence. Here again it may be well to distinguish two forms which this contention may assume: (1) Purpose in nature if such there be falls outside the naturalistic universe of discourse; (2) such a conception is therefore inadmissible. It is a picturesque relic of the childhood of our race.
We have here what may, I think, be regarded as the radical and fundamental distinction between two opposing and often strongly antagonistic modes of interpreting nature. On the one hand, the human mind, will, purpose, is taken as the basis of interpretation, and in such terms is the meaning of nature explained. On the other hand, the phenomena of nature, as formulated by science, afford, it is said, the only valid foundations on which we can securely build, and in such terms is the human mind itself explained. In the one case, the course of procedure is from within outwards, until all nature is pervaded by mind analogous to that which interprets. In the other case, the course of procedure is from without inwards, until the mind is explained as the product of molecular motion of a peculiar and exceedingly intricate kind. Let us briefly trace the origin of these two types of interpretation.