likened to the inheritance of specific drafts for definite needs which are sure to arise in the conduct of life; the latter to the inheritance of a legacy which may be drawn upon for any purpose as occasion may demand. If the need becomes habitual the animal may, so to speak, instruct his banker to set aside a specific sum to meet it as it arises. But this arrangement is a purely individual matter, dictated by experience, and in no wise enjoined by the original terms of the bequest. And both types are fostered by natural selection which develops (a) such congenital definiteness of response, and (b) such innate plasticity, as are advantageous under the conditions of existence; uniform conditions tending to emphasize the former, variable conditions the latter. Difficult as it may be to earmark the items of the organic bequest to say that, of the sum of energy expended in any given case of organic behaviour, so much is due to a specific draft definitely assigned in heredity for this particular purpose, and so much is contributed from the general legacy of innate plasticity, it none the less conduces to clear thinking to emphasize the logical distinction between them, so long as it is steadily borne in mind that logical distinction does not imply biological separation. The animal, with all its varied modes of behaviour, is an organic whole, and as an organic whole it has been developed from the fertilized egg. The very same tissues which exhibit congenital modes of behaviour are capable also of acquiring new responses and playing their part in accommodation. We have not one set of organs which are the products of variation and another set which result from modification. Our study would no doubt be simplified if this were the case; but it is not so. And we must take the animal as we find it, presenting varied behaviour of complex origin. Even the reflex nervous centres, which are concerned in responses so automatic as to suggest a stereotyped structure of distinctively germinal origin, are also, as we saw at the close of the last section, in close touch with those centres of control which are associated with the supreme power of accommodation arising from the possession of consciousness. CHAPTER II CONSCIOUSNESS I. THE CONSCIOUS ACCOMPANIMENTS OF CERTAIN ORGANIC CHANGES It is possible that all organic behaviour is accompanied by consciousness. But there is no direct means of ascertaining whether it is so or not. This is, and must remain, a matter of more or less plausible conjecture. We have, indeed, no direct knowledge of any consciousness save our own. Undue stress should not, however, be laid on this fundamental isolation of the individual mind. We confidently infer that our fellowmen are conscious, because they are in all essential respects like us, and because they behave just as we do when we act under its guiding influence. And on similar grounds we believe not less confidently that many animals are also conscious. But how far we are justified in extending this inference it is difficult to say. Probably our safest criterion is afforded by circumstantial evidence that the animal in question profits by experience. If, as we watch any given creature during its life-history, we see at first a number of congenital or acquired modes of behaviour, we may not be able to say whether they are accompanied by consciousness or not; but if we find that some of these are subsequently carried out more vigorously while others are checked, we seem justified in the inference that pleasurable consciousness was associated with the results of the former, and disagreeable consciousness with those of the latter. When we see that a chick, for example, pecks at first at any small object, it is difficult to say, on these grounds, whether it is a sentient animal or only an unconscious automaton; and if it continued to behave in a similar fashion throughout life, our difficulty would still remain. But when we see that some objects are rejected while others are selected, we infer that consciousness in some way guides its behaviour. The chick has profited by experience. But even this is clearly only a criterion of what we may term effective consciousness. There may be sentience which is merely an accompaniment of organic action without any guiding influence on subsequent modes of behaviour. In that case it is not effective; and whether it is present or not we have no means of ascertaining. We seem also to be led to the conclusion, both from a priori considerations and from the results of observation, that effective consciousness is associated with a nervous system. Its fundamental characteristic is control over the actions, so that some kinds of behaviour may be carried out with increased vigour, and others checked. And it is difficult to see how this can take place unless the centres of control are different from those over which they exercise this influence. If we are to understand anything definite by the guidance of consciousness, we must conceive it as standing apart from and exercising an overruling influence over that which it guides. This is unquestionably an essential characteristic of consciousness, as generally understood by those who take the trouble to consider its relation to behaviour; and though some would seek to persuade us that a mere accompaniment of consciousness can somehow determine the continuance or discontinuance of organic behaviour, it is difficult to see how this can be the case. The accompaniment of air-tremors can no more influence the vibrations of a sounding string than an accompaniment of consciousness can affect the nature of the organic changes in the tentacles of the Sun-dew leaf. And if, instead of trusting to such general a priori considerations, we study with attention the conditions under which an animal so behaves as to lead us to infer that it profits by experience, we find that it is not the consciousness that accompanies the behaviour which leads to future guidance, but the consciousness that arises from the results of the behaviour. Let us willingly grant that the newly hatched, and as yet inexperienced chick, when it pecks at a small object is conscious of a visual impression, and is conscious also of movements of its neck and beak. These do not constitute the experience by which it profits. This is provided by the results of the pecking, according as the morsel seized is nice or nasty. We may say, in popular language, that the little bird remembers when it sees a similar object that the former results were pleasant or distasteful, as the case may be; and that it is through this remembrance that future guidance is rendered possible. But all the evidence that we possess goes to show that the sensory centres, stimulated by what we will assume to be the taste of the morsel, are different from those which are affected by sight, and the movements concerned in pecking. So that the consciousness which is effective in guiding future action is an accompaniment of the stimulation of centres that are different from those concerned in the behaviour over which guidance is exercised. And if this interpretation of the observed facts be correct, it supports the conclusions reached from a priori considerations. It seems further to show that, not only is a nervous system necessary for the occurrence of controlled behaviour, but that no little complexity in its intercommunications is essential. It may be urged that the chick's behaviour which has been selected for purposes of illustration, and the interpretation we have put upon it, throws too much stress on remembrance, so called, and further gives the false impression that all experience must be for future guidance. There are surely numberless cases, it will be said, in which nothing of the nature of distinct memory is involved, and in which the guidance of consciousness is exercised at once over present behaviour, without any postponement to the future. Even omitting for the present the former point, the formula implied -that present experience is for future guidance-cannot be accepted in view of the familiar fact that present experience is constantly influencing present behaviour. Practically speaking, this is perfectly true: because, practically, under the term present we include quite an appreciable period of timesay, a few seconds, or even minutes. If we narrow our conception of the present, as is commonly done in philosophical discussions, to the boundary line between past and future, then it will be seen that even the guidance of what in popular speech is called present behaviour is really exercised on the subsequent phases of that behaviour. At the risk of some technicality our position must be explained a little more fully. It is assumed that the data of consciousness are afforded by afferent impulses coursing inwards from the organs of special sense, or those concerned in responsive movements. This conclusion rests on such a wide body of psychological inference that it may be accepted without discussion, at any rate for our immediate purpose. The efferent impulses, those which effect the orderly contraction of the muscles, are unconscious; but when the movement is produced afferent impulses course inwards from the parts concerned in the behaviour, and these may then contribute data to consciousness. Now let us suppose that a chick, which has been hatched in an incubator, be removed some twelve hours after birth, held in the hands for a few minutes until its eyes have grown accustomed to the light, and placed on a table near some small pieces of hard-boiled egg. Let us watch its behaviour and endeavour to interpret it. We shall have occasion to consider hereafter whether the conscious experience of parents and ancestors is inherited as such; for the present we will assume that it is not. The chick has to acquire for itself its own experience. A piece of egg catches the eye of the little bird, which then pecks at it, and just fails to seize it. Here is a piece of congenital organic behaviour. Taken by itself one might find it difficult to say whether it is accompanied by consciousness or not, just as one finds it difficult to say whether the closure of the Venus's Fly-trap is conscious. But the subsequent behaviour of the chick leads us to infer that it is a sentient animal; and we may, therefore, fairly assume that it |