fusing to manufacture organic out of inorganic material and taking organic substances ready made from organ- isms that had turned toward the vegetative life, so, among the aoimal species themselves, many contrived to live at the expense of other animals. For an organism that is animal, that is to say mobile, can avail itself of its mobihty to go in search of defenseless animals, and feed on them quite as well as on vegetables. So, the more species be- came mobile, the more they became voracious and danger- ous to one another. Hence a sudden arrest of the entire animal world in its progress towards higher and higher mobihty; for the hard and calcareous skin of the echino- derm, the shell of the mollusc, the carapace of the crustacean and the ganoid breast-plate of the ancient fishes probably all originated in a common effort of the animal species to protect themselves against hostile species. But this breast-plate, behind which the animal took shelter, constrained it in its movements and sometimes fixed it in one place. If the vegetable renounced consciousness in wrapping itself in a cellulose membrane, the animal that shut itself up in a citadel or in armor condemned itself to a partial slumber. In this torpor the echinoderms fljid even the molluscs live to-day. Probably arthropods and vertebrates were threatened with it too. They escaped, however, and to this fortunate circumstance is due the expansion of the highest forms of life.
In two directions, in fact, we see the impulse of life
to movement getting the upper hand again. The fishes
exchanged their ganoid breast-plate for scales. Long
before that, the insects had appeared, also disencumbered
of the breast-plate that had protected their ancestors.
Both supplemented the insufSciency of their protective
covering by an agility that enabled them to escape their
enemiee. and also to assume tbe offensive, to choose the
ICHIP.
place and the moment of encounter. We see a progress of the same kind in the evolution of human armaments, The first impulse is to seek shelter; the second, which is the better, is to become as supple as possible for flight and above all for attack — attack being the most effective means of defense. So the heavy hoplite was supplanted by the legionary; the kaight, clad in annor, had to give place to the light free-moving infantrj'man ; and in a general way, in the evolution of life, just as in the evo- lution of human societies and of individual destinies, the greatest successes have been for those who have accepted the heaviest risks.
Evidently, then, it was to the animal's interest to make itself more mobile. As we said when speaking of adaptation in general, any transformation of a species can be explained by its own particular interest. This will give the immediate cause of the variation, but often only the most superficial cause. The profound cause is the impulse which thrust hfe into the world, which made it divide into vegetables and animals, which shunted the animal on to suppleness of form, and which, at a certain moment, in the animal kingdom threatened with torpwr, secured that, on some points at least, it should rouse itself up and move forward.
On the two paths along which the vertebrate* and arthropods have separately evolved, development {apart from retrogressions connected with parasitism or any other cause) has consisted above all in the progress of the aensori-motor ner\-ou8 system. Mobility and sup- plensBS were sought for, and also — through many experi- mental attempts, and not without a tendency to excess of substance and brute force at the start — variety of move- ments. But this quest itself took place in divergent directions. A glance at the nervous system of the arthro-
pods and that of the vertebrates shows us the difference. In the arthropods, the body is formed of a aeries more or less long of rings set together; motor activity ia thus distributed amongst a varying — sometimes a considerable — number of appendages, eacti of which has its special function. In the vertebrates, activity is concentrated in two pairs of members only, and these organs perform functions which depend much less strictly on their form.' The independence becomes complete in man, whose hand is capable of any kind of work.
That, at least, is what we see. But behind what is
seen there is what may be surmised — two powers, im-
manent in life and originally intermingled, which were
bound to part company in course of growth.
To define these powers, we must consider, in the evo-
lution both of the arthropods and the vertebrates, the
Bpecies which mark the culminating point of each. How
is this point to be determined? Here again, to aim at
geometrical precision will lead us astray. There is no
eingle simple sign by which we can recognize that one
species is more advanced than another on the same line
of evolution. There are manifold characters, that must
be compared and weighed in each particular case, in order
to ascertain to what extent they are essential or acci-
dental and how far they must be taken into account.
It is unquestionable, for example, that success is the most general criterion of superiority, the two terms being, up to a certain point, synonymous. By success must be understood, so far as the living being is concerned, an aptitude to develop in the most diverse environments, through the greatest possible variety of obstacles, so as to cover the widest possible extent of ground. A speciea
8m, on this subject, Shftler, The Individual, New Vork, 1600, pp. Ilft-126.
which claims the entire eeirth for its domain is truly a dominating and consequently superior species. Such is the human species, which represents the culminatmg poiot of the evolution of the vertebrates. But such also are, in the series of the articulate, the insects and in partic- ular certain hymenoptera. It has been said of the anta that, as man is lord of the soil, they are lords of the sub-aoil.
On the other hand, a group of species that has appeared
late may be a group of degenerates; but, for that, some
special cause of retrogression must have intervened.
By right, this group should be superior to the group from
which it is derived, since it would correspond to a more
advanced stage of evolution. Now man is probably
the latest comer of the vertebrates;' and in the insect
series no species is later than the hymenoptera, unless
it be the lepidoptera, which are probably degenerates,
living parasitically on flowering plants.
So, by different ways, we are led to the same conclusion. The evolution of the arthropods reaches its culminating point in the insect, and in particular in the hymenoptera, as that of the vertebrates in man. Now, since instinct is nowhere so developed as in the insect world, and in no group of Uiseets so marvelously as in the hymenoptera, it may be said that the whole evolution of the animal king- dom, apart from retrogressions towards vegetative life, has taken place on two divergent paths, one of which led to instinct and the other to intelligence.
This point is disputed by M. Rcn£ Quintou, who regards the car- nivonius and ruminant mammatH, an well as certein biids, as subse- quent to man (R. Qmntan, L'Kaudemer milieu organique, Paris, 1904, p. 43S). We may nay bore that our general conclusiooa, altbough very different from M. Quinton's, are not irraconcilablB with them; for if evolution has really been such as we represent it, the vertebrates must have made an effort to maintain themselves in the most favor- able conditions of activity — the veiy conditions, indeed, which life luhd eh^>flen in the b^iiuuns.
n.j DEVELOPMENT OF ANIMAL LIFE 135
Vegetative torpor, instinct, and intelligence — these, then, are the elements that coiocided in the vital impulsion common to plants and animals, and which, in the course of a development in which they were made manifest in the most unforeseen forms, have been dissociated by the very fact of their growth. Tlie cardinal error which, from Aristotle onwards, has vitiated most of the philosophies of Tiaiure, is to see in vegetaiive, instinctive and rational life, three successive degrees of the development of one and the same tendency, whereas they are three divergent directions of an adimty that has split up as il grew. The difference between them is not a difference of intensity, nor, more generally, of degree, but of kind.
It is important to investigate this point. We have
seen in the case of vegetable and animal life how they
are at once mutually complementary and mutually an-
tagonistic. Now we must show that intelligence and /
instinct also are opposite and complementary. But i
let us first ejtplain why we are generally led to regard
them as activities of which one is superior to the other
and based upon it, whereas in reality they are not things
of the same order: they have not succeeded one another,
nor can we assign to them differentj grades.
It is because intelligence and instinct, having origin- 1 ally been interpenetrating, retain something of their I common origin. Neither is ever found in a pure state. We said that in the plant the consciousness and mobihty of the animal, which lie dormant, can be awakened; and that the animal lives under the constant menace of being drawn aside to the vegetative hfe. The two tendencies — that of the plant and that of the animal — were so thor- oughly interpenetrating, to begin with, that there has never been a complete severance between them: thqr
138 CREATIVE EVOLUTION mArT
haunt each other continually; everywhere we find them mingled; it is the proportion that differs. So with in- telligence and instinct. There is no intelligence in which some traces of instinct are not to be discovered, more especially no instinct that is not surrounded with a fringe of intelligence. It is this fringe of intelligence that has been the cause of so many misunderstandings. From the fact that instinct is always more or less in- telligent, it has been concluded that instinct and intelligence are things of the same kind, that there is only a difference of complexity or perfection between them, and, above all, that one of the two is expressible in terms of the other. In reaUty, they accompany each other only because they are complementary, and they are complementary only because they are different, what is instinctive in instinct being opposite to what is intelligent in intelligence.
We are bound to dwell on this point. It is one of the utmost importance.
Let us say at the outset that the distinctions we are going to make will be too sharply drawn, just, because we wish to define in instinct what is instinctive, and in intelh- gence what is intelligentj whereas all concrete instinct is mingled with intelligence, as all real intelligence is pene- trated by instinct. Moreover, neither intelligence nor instinct lends itself to rigid definition: they are tendencies, and not things. Also, it must not be forgotten that in the present chapter we are considering intelligence and instinct as going out of life which deposits them along its course. Now the life manifested by an organism is, in our view, a certain effort to obtain certain things from the material world. No wonder, therefore, if it is the diversity of this effort that strikes us in instinct and intelligence, and if we see in these two modes of psychical activity, above all else, two different methods of action on inert matter.
n.i
This rather narrow view of them has the advantage of ^ving us an objective means of distinguishing them. In return, however, it gives us, of intelHgence in general and of instinct in general, only the mean position above and below which both constantly oscillate. For that reason the reader must expect to see in what follows only a dia- grammatic drawing, in which the respective outlines of intelligence and instinct are sharper than they should be, and in which the shading-off which comes from the indecision of each and from their reciprocal encroachment on one another is neglected. In a matter so obscure, we cannot strive too hard for clearness. It will always be easy afterwards to soften the outlines and to correct what is too geometrical in the drawing — in short, to replace the rigidity of a diagram by the suppleness of life.