According to this way of thinking, there is a certain looseness about the relation of the common material nature to the higher forms of organization capable of capturing it. Considered in itself alone, it is perhaps to be seen as governed by absolutely determined laws of its own. It is heavy, then it will fall unless obstructed; it is solid, then it will resist intrusions. But considered as material for organization by higher forms, it is indeterminate. It acts in one sort of way under the persuasion of the sheep-form, and in another sort of way under the persuasion of the dog-form, and we cannot tell how it will act until we know which form is going to capture it. No amount of study bestowed on the common material nature will enable us to judge how it will behave under the persuasion of the higher organizing form. The only way to discover that is to examine the higher form itself.
Every form, then, will really be the object of a distinct science. The form of the sheep and the form of the dog have much in common, but that merely happens to be so; we cannot depend upon it, or risk inferences from sheep to dog: we must examine each in itself; we shall really need a science of probatology about sheep, and cynology about dogs. Again, the common material nature has its own principles of being and action, so it will need a science of itself, which we may call hylology. Each of these sciences is mistress in her own province; but how many there are, and how puzzlingly they overlap! So long as we remain within the province of a single science, we may be able to think rigorously, everything will be 'tight'. But as soon as we consider border-issues between one province and another, farewell to exactitude: everything will be 'loose'. We can think out hylology till we are blue in the face, but we shall never discover anything about the entry of material elements into higher organizations, or how they behave when they get there. We may form perfect definitions and descriptions of the form of the dog as such, and still derive no rules for telling what elements of matter will enter into the body of a given dog or how they will be placed when they do. All we can be sure of is, that the dog-form will keep itself going in, and by means of, the material it embodies—unless the dog dies. But what happens to the matter in the body of the dog is 'accidental' to the nature of the matter; and the use of this matter, rather than of some other equally suitable, is accidental to the nature of the dog.
No account of material events can dispense with accidental relations altogether. We must at least recognize that there are accidental relations between particular things. Accident in the sense of brute fact had to be acknowledged even by the tidiest and most dogmatic atomism of the last century. That atomism must allow it to be accidental, in this sense, that the space surrounding any given atom was occupied by other atoms in a given manner. It belonged neither to the nature of space to be occupied by just those atoms in just those places, nor to the nature of the atoms to be distributed just like that over space; and so in a certain sense the environment of any atom was an accidental environment. That is, the particular arrangement of the environment was accidental. The nature of the environment was not accidental at all. It was proper to the nature of the atom to be in interaction with other atoms over a spatial field, and it never encountered in the fellow-denizens of space any other nature but its own. It was not subject to the accident of meeting strange natures, nor of becoming suddenly subject to strange or unequal laws of interaction. All interactions, being with its own kind, were reciprocal and obedient to a single set of calculable laws.
But the medieval philosophy had asserted accidental relations between distinct sorts of natures, the form of living dog and the form of dead matter, for example. No one could know a priori what effect an accidental relation would produce, and all accidental relations between different pairs of natures were different: at the most there was analogy between them. Every different nature had to be separately observed, and when you had observed them all, you could still simply write an inventory of them, you could not hope to rationalize your body of knowledge. Let us narrow the field and consider what this doctrine allows us to know about the wood of a certain kind of tree. We shall begin by observing the impressions it makes on our several senses, and we shall attribute to it a substantial form such as naturally to give rise to these impressions, without, perhaps, being so rash as to claim a knowledge of what this substantial form is. Still we do not know what its capacities of physical action and passion may be. We shall find them out by observing it in relation to different 'natures'. It turns out to be combustible by fire, resistant to water, tractable to the carpenter's tools, intractable to his digestive organs, harmless to ostriches, nourishing to wood-beetles. Each of these capacities of the wood is distinct; we cannot relate them intelligibly to one another, nor deduce them from the assumed fundamental 'woodiness'.
We can now see why 'substantial forms' were the bêtes noires of the seventeenth-century philosophers. It was because they turned nature into an unmanageable jungle, in which trees, bushes, and parasites of a thousand kinds wildly interlaced. There was nothing for it, if science was to proceed, but to clear the ground and replant with spruce in rows: to postulate a single uniform nature, of which there should be a single science. Now neither probatology nor cynology could hope to be universal—the world is not all sheep nor all dog: it would have to be hylology; for the world is, in its spatial aspect, all material. Let us say, then, that there is one uniform material nature of things, and that everything else consists in the arrangements of the basic material nature; as the show of towers and mountains in the sunset results simply from an arrangement of vapours. And let us suppose that the interactions of the parts of matter are all like those which we can observe in dead manipulable bodies—in mechanism, in fact. Such was the postulate of the new philosophers, and it yielded them results.
It yielded them results, and that was highly gratifying. But what, meanwhile, had happened to those palpable facts of common experience from which the whole philosophy of substantial forms had taken its rise? Is the wholeness of a living thing the mere resultant of the orderly operations of its parts? Is a bee no more essentially one than a swarm is? Is the life of a living animal indistinguishable from the rhythm of a going watch, except in degree of complication and subtlety of contrivance? And if an animal's body, say my own, is simply an agglomerate of minute interacting material units, and its wholeness is merely accidental and apparent, how is my conscious mind to be adjusted to it? For my consciousness appears to identify itself with that whole vital pattern which used to be called the substantial form. We are now told that the pattern is nothing real or active, but the mere accidental resultant of distinct interacting forces: it does no work, it exercises no influence or control, it is nothing. How then can it be the vehicle and instrument of my conscious soul? It cannot. Then is my soul homeless? Or is it to be identified with the activity and fortunes of a single atomic constituent of my body, a single cog in the animal clockwork? If so, how irrational! For the soul does not experience itself as the soul of one minute part, but as the soul of the body.
Such questions rose thick and fast in the minds of the seventeenth-century philosophers. It will cause us no great surprise that Leibniz should have quickly felt that the Formal Principle of Aristotle and of the Scholastic philosophy must be by hook or by crook reintroduced—not as the detested substantial form, but under a name by which it might hope to smell more sweet, entelechy.
Nothing so tellingly revealed the difficulties of the new philosophy in dealing with living bodies as the insufficiency of the solutions Descartes had proposed. He had boldly declared the unity of animal life to be purely mechanical, and denied that brutes had souls at all, or any sensation. He had to admit soul in man, but he still denied the substantial unity of the human body. It was put together like a watch, it was many things, not one: if Descartes had lived in our time, he would have been delighted to compare it with a telephone system, the nerves taking the place of the wires, and being so arranged that all currents of 'animal spirit' flowing in them converged upon a single unit, a gland at the base of the brain. In this unit, or in the convergence of all the motions upon it, the 'unity' of the body virtually consisted; and the soul was incarnate, not in the plurality of members (for how could it, being one, indwell many things?), but in the single gland.
Even so, the relation between the soul and the gland was absolutely unintelligible, as Descartes