its changing motions to the changing motions of a pigeon, so as eventually to strike it: the adjustment of inner relations to outer relations is manifest. Here is a boy in an epileptic fit. Between his struggles and the co-existences and sequences around him there is no correspondence whatever. Yet his movements betray vitality just as much as do the movements of the hawk. Both exhibit that principle of activity which constitutes the essential element in our conception of life.
§ 36b. Evidently, then, the preceding chapters recognize only the form of our conception of life and ignore the body of it. Partly sufficing as does the definition reached to express the one, it fails entirely to express the other. Life displays itself in ways which conform to the definition; but it also displays itself in many other ways. We are obliged to admit that the element which is common to the two groups of ways is the essential element. The essential element, then, is that special kind of energy seen alike in the usual classes of vital actions and in those unusual classes instanced above.
Otherwise presenting the contrast, we may say that due attention has been paid to the connexions among the manifestations, while no attention has been paid to that which is manifested. When it is said that life is "the definite correspondence of heterogeneous changes, both simultaneous and successive, in correspondence with external co-existences and sequences," there arises the question – Changes of what? Within the body there go on many changes, mechanical, chemical, thermal, no one of which is the kind of change in question; and if we combine in thought so far as we can these kinds of changes, in such wise that each maintains its character as mechanical, chemical, or thermal, we cannot get out of them the idea of Life. Still more clearly do we see this insufficiency when we take the more abstract definition – "the continuous adjustment of internal relations to external relations." Relations between what things? is the question then to be asked. A relation of which the terms are unspecified does not connote a thought but merely the blank form of a thought. Its value is comparable to that of a cheque on which no amount is written. If it be said that the terms cannot be specified because so many heterogeneous kinds of them have to be included, then there comes the reply that under cover of this inability to make a specification of terms that shall be adequately comprehensive, there is concealed the inability to conceive the required terms in any way.
Thus a critical testing of the definition brings us, in another way, to the conclusion reached above, that that which gives the substance to our idea of Life is a certain unspecified principle of activity. The dynamic element in life is its essential element.
§ 36c. Under what form are we to conceive this dynamic element? Is this principle of activity inherent in organic matter, or is it something superadded? Of these alternative suppositions let us begin with the last.
As I have remarked, in another place, the worth of an hypothesis may be judged from its genealogy; and so judged the hypothesis of an independent vital principal does not commend itself. Its history carries us back to the ghost-theory of the savage. Suggested by experiences of dreams, there arises belief in a double – a second self which wanders away during sleep and has adventures but comes back on waking; which deserts the body during abnormal insensibility of one or other kind; and which is absent for a long period at death, though even then is expected eventually to return. This indwelling other-self, which can leave the body at will, is by-and-by regarded as able to enter the bodies of fellow men or of animals; or again, by implication, as liable to have its place usurped by the intruding doubles of fellow men, living or dead, which cause fits or other ills. Along with these developments its quality changes. At first thought of as quite material it is gradually de-materialized, and in advanced times comes to be regarded as spirit or breath; as we see in ancient religious books, where "giving up the ghost" is shown by the emergence of a small floating figure from the mouth of a dying man. This indwelling second self, more and more conceived as the real self which uses the body for its purposes, is, with the advance of intelligence, still further divested of its definite characters; and, coming in mediæval days to be spoken of as "animal spirits," ends in later days in being called a vital principle.
Entirely without assignable attributes, this something occurs in thought not as an idea but as a pseud-idea (First Principles, Chap. II). It is assumed to be representable while really unrepresentable. We need only insist on answers to certain questions to see that it is simply a name for an alleged existence which has not been conceived and cannot be conceived.
1. Is there one kind of vital principle for all kinds of organisms, or is there a separate kind for each? To affirm the first alternative is to say that there is the same vital principle for a microbe as for a whale, for a tape-worm as for the person it inhabits, for a protococcus as for an oak; nay more – is to assert community of vital principle in the thinking man and the unthinking plant. Moreover, asserting unity of the vital principle for all organisms, is reducing it to a force having the same unindividualized character as one of the physical forces. If, on the other hand, different kinds of organisms have different kinds of vital principles, these must be in some way distinguished from one another. How distinguished? Manifestly by attributes. Do they differ in extension? Evidently; since otherwise that which animates the vast Sequoia can be no larger than that which animates a yeast-plant, and to carry on the life of an elephant requires a quantity of vital principle no greater than that required for a microscopic monad. Do they differ otherwise than in amount? Certainly; since otherwise we revert to the preceding alternative, which implies that the same quality of vital principle serves for all organisms, simple and complex: the vital principle is a uniform force like heat or electricity. Hence, then, we have to suppose that every species of animal and plant has a vital principle peculiar to itself – a principle adapted to use the particular set of structures in which it is contained. But dare anyone assert this multiplication of vital principles, duplicating not only all existing plants and animals but all past ones, and amounting in the aggregate to some millions?
2. How are we to conceive that genesis of a vital principle which must go along with the genesis of an organism? Here is a pollen-grain which, through the pistil, sends its nucleus to unite with the nucleus of the ovule; or here are the nuclei of spermatozoon and ovum, which, becoming fused, initiate a new animal: in either case failure of union being followed by decomposition of the proteid materials, while union is followed by development. Whence comes that vital principle which determines the organizing process? Is it created afresh for every plant and animal? or, if not, where and how did it pre-exist? Take a simpler form of this problem. A protophyte or protozoon, having grown to a certain size, undergoes a series of complex changes ending in fission. In its undivided state it had a vital principle. What of its divided state? The parts severally swim away, each fully alive, each ready to grow and presently to subdivide, and so on and so on, until millions are soon formed. That is to say, there is a multiplication of vital principles as of the protozoa animated by them. A vital principle, then, both divides and grows. But growth implies incorporation of something. What does the vital principle incorporate? Is it some other vital principle external to it, or some materials out of which more vital principle is formed? And how, in either case, can the vital principle be conceived as other than a material something, which in its growth and multiplication behaves just as visible matter behaves?
3. Equally unanswerable is the question which arises in presence of life that has become latent. Passing over the alleged case of the mummy wheat, the validity of which is denied, there is experimental proof that seeds may, under conditions unfavourable to germination, retain for ten, twenty, and some even for thirty years, the power to germinate when due moisture and warmth are supplied. (Cf. Kerner's Nat. Hist. of Plants, i, 51-2). Under what form has the vital principle existed during these long intervals? It is a principle of activity. In this case, then, the principle of activity becomes inactive. But how can we conceive an inactive activity? If it is a something which though inactive may be rendered active when conditions favour, we are introduced to the idea of a vital principle of which the vitality may become latent, which is absurd. What shall we say of the desiccated rotifer which for years has seemed to be nothing more than a particle of dust, but which now, when water is supplied, absorbs it, swells up, and resumes those ciliary motions by which it draws in nutriment? Was the vital principle elsewhere during
