There is hardly any human action, feeling, or belief, which has not been ranged under the term instinct. Hunger and thirst have been called instincts; so have the faculty of speech, the use of the right hand in preference to the left, the love of society, the desire to possess property, the desire to avoid danger and prolong life, and the belief in supernatural agencies, upon which is engrafted the religious sentiment. We cannot, in this paper, attempt to analyze these and many other similar examples which have been given as illustrations of instinct in treatises of high repute, and show that they do not at all come within that class of actions which we contrast with reason. In regard to those actions of early infancy which have often been adduced as illustrations of instinct, the physiologists of the present day are agreed that they are as mechanical as the act of breathing. To place these upon the same level with the complex and wonderful operations of the bee, the ant, and the beaver, is to admit that the instincts of the latter are merely reflex actions following impressions on the nerves of sense.

On the other hand, whether the animals inferior to man ever exercise any conscious process of reasoning is a question which has often been discussed, and upon which there is no general agreement. Instances of the remarkable sagacity of some domesticated animals are often adduced as proofs of reasoning on their part. Some of these wonderful feats may be traced to the unconscious faculty of imitation, which even in man often appears as a blind propensity, although he exercises an active and rational imitation as well. Sometimes the mere association of ideas, or the perception by animals that one thing is accompanied by another or that one event follows another, is mistaken for that higher principle which in man judges, reflects, and understands causes and effects. When the dog sees his master take down his gun, his blandishments show that he anticipates a renewal of the pleasures of the chase. He does not reflect upon past pleasures; but, seeing the gun in his master's hand, a confused idea of the feelings that were associated with the gun in times past is called up. So the ox and the horse learn to associate certain movements with the voice and gesture of man. And so a fish, about the most stupid of all animals, comes to a certain spot at a certain signal to be fed. These combinations are quite elementary. This is quite another thing from that reciprocal action of ideas on each other by which man perceives the relations of things, understands the laws of cause and effect, and not only forms judgments of the past, but draws conclusions which are laws for the future. We find in the brute no power of attending to and arranging its thoughts,—no power of calling up the past at will and reflecting upon it. The animal has the faculty of memory, and, when this is awakened, the object remembered may be accompanied by a train or attendance of accessory notions which have been connected with the object in the animal's past experience. But it never seems to be able to exercise the purely voluntary act of recollection. It is not capable of comparing one thing with another, so far as we can judge. If the animal could exercise any true act of comparison, there would be no limit to the exercise of it, and the animal would be an intelligent being; for the result of a simple act of comparison is judgment, and reasoning is only a double act of comparison. We have the authority of Sir William Hamilton for saying that the highest function of mind is nothing higher than comparison. Hence comes thought,—hence, the power of discovering truth,—and hence, the mind's highest dignity, in being able to ascend unassisted to the knowledge of a God. Those who hold that the minds of the inferior animals are essentially of the same nature with that of the human race, and differ only in degree, should reflect that the distinguishing attribute of the human mind does not admit of degrees. The faculty of comparison, in all its various applications, must be either wholly denied or else wholly attributed. Hence, Pope is not philosophical, when he applies the epithet "half-reasoning" to the elephant. "As reasoning," says Coleridge, "consists wholly in a man's power of seeing whether any two ideas which happen to be in his mind are or are not in contradiction with each other, it follows of necessity, not only that all men have reason, but that every individual has it in the same degree." We gather also from the same acute writer that in the simple determination, "black is not white," all the powers are implied that distinguish man from other animals. If, then, the brute reasoned at all, he would be a rational being, and would improve and gain knowledge by experience; and, moreover, he would be a moral agent, accountable for his conduct. "Would not the brute," asks an able writer in the "Zoölogical Journal," "take a survey of his lower powers, and would he not, as man does, either rightly use or pervert them, at his pleasure?"

It has been suggested by some one, that, by the law of merciful adaptation, which extends throughout the universe, thought would not be imprisoned and pent up forever in an intelligence wanting the power of expression. But it is also to be noticed that the want of an articulate language or a system of general signs puts it out of the power of animals to perform a single act of reasoning. The use of language to communicate wants and feelings is not peculiar to "word-dividing men," though enjoyed by them in a much higher degree than by other animals. Doubtless every species of social animals has some kind of language, however imperfect it may be. "We never watch the busy workers of the ant-hill," says Acheta Domestics, (the author of "Episodes of Insect-Life,") "stopping as they encounter and laying their heads together, without being pretty certain that they are saying to each other something quite as significant as 'Fine day.'" And when the morning wakes the choral song of the birds, they seem to be telling each other of their happiness. But though animals have a language appropriate to the expression of their sensations and emotions, they have no words, "those shadows of the soul, those living sounds." Words are symbols of thoughts, and may be considered as a revelation of the human mind. It is this use of language as an instrument of thought, as a system of general signs, which, according to Bishop Whately, distinguishes the language of man from that of the brute; and the same eminent authority declares that without such a system of general signs the reasoning process could not be conducted.

It is true, that we often see in the inferior animals manifestations of deductions of intellect similar to those of the human mind,—only that they are not made by the animals themselves, but for them and above their conscious perception. "When a bee," says Dr. Reid, "makes its combs so geometrically, the geometry is not in the bee, but in that great Geometrician who made the bee, and made all things in number, weight, and measure." Since the animal is not conscious of the intelligence and design which are manifested in its instincts, which it obeys and works out, the conscious life of the individual must be wholly a life within the senses. The senses alone can give the animal only an empirical knowledge of the world of its observation. The senses may register and report facts, but they can never arrive at an understanding of necessary truths; the source of this kind of knowledge is the rational mind, which has an active disposition to draw out these infallible laws and eternal truths from its own bosom. The main tendency of the rational mind is not towards mere phenomena, but their scientific explanation. It seeks to trace effects, as presented to us by the senses, back to the causes which produced them; or contemplating things wholly metaphysical, it seeks to follow out the laws which it has itself discovered, till they have gone through a thousand probable contingencies and lost themselves in numberless results. It is on account of this capacity and tendency of the human mind to look through fact to law, through individuals to classes, through effects to causes, through phenomena to general principles, that the late Dr. Burnap was led to declare, in a very interesting course of lectures which he delivered before the Lowell Institute a few years since, that he considered the first characteristic difference between the highest species of animals and the lowest race of man to be a capacity of science. But is not the whole edifice of human science built upon the simple faculty of comparison?

This is the ultimate analysis of all the highest manifestations of the human mind, whether of judgment, or reason, or intellect, or common sense, or the power of generalization, or the capacity of science. We have already quoted Hamilton to this effect, and we, moreover, have his authority for saying that the faculty of discovering truth, by a comparison of the notions we have obtained by observation and experience, is the attribute by which man is distinguished as a creature higher than the animals. We might also cite Leibnitz to the effect that men differ from animals in being capable of the formation of necessary judgments, and hence capable of demonstrative sciences.

But notwithstanding it seems so apparent that what is customarily called reason is the distinguishing endowment which makes man the "paragon of animals," we very often meet with attempts to set up some other distinction. We cannot here go into an examination of these various theories, or even allude to them specially. We will, however, briefly refer to a view which was recently advanced in one of our leading periodicals, inasmuch as it makes prominent a distinction which we wish to notice, although it seems to us to be only subordinate to the distinguishing attribute of the human mind which we have already pointed out. It is said that self-consciousness is what makes the great difference between man and other animals; that the latter do not separate themselves consciously from the world in which they exist; and that, though they have emotions, impulses, pains, and pleasures, every change of feeling in them takes at once the form of an outward change either in place or position. It is not intended, however, to be said that they have no conscious perception of external things. We cannot possibly conceive of an animal without this condition of consciousness. A consciousness of an outward world is an essential quality of the animal soul; this distinguishes the very lowest form of animal life from the vegetable world; and hence it cannot possibly be, as has been suggested by some, that there are any animate beings which have no endowments superior to those which belong to plants. The plant is not conscious of an outward world, when it sends out its roots to obtain the nourishment which is fitting for itself; but the polype, which is fixed with hundreds of its kind on the same coral-stock, and is able only to move its mouth and tentacles, is aware of the presence of the little craw-fish upon which it feeds, and throws out its lasso-cells and catches it. The world of which the polype has any perception is not a very large one. The outer world of a bird is vastly greater; and man knows a world without, which is immeasurably large beyond that of which any other animal is conscious, because both his physical organs and his mental faculties bring him into far the most diversified and intimate relations with all created things. He sees in every flower of the garden and every beast of the field, in the air and in the sea, in the earth beneath his feet and in the starry heavens above him, countless meanings which are hidden to all the living world besides. To him there is a world which has existed and a world that will exist. "Man," says Protagoras, "is the measure of the universe." But he has a greater dignity in being able to apprehend the world of thought within. "Whilst I study to find how I am a microcosm or little world," says Sir Thomas Browne, "I find myself something more than the great." Man can make himself an object to himself and gain the deepest insight into the workings of his own mind. This internal perception seems never to be developed in other animals. We have already observed that they have no thought of their own. The intelligence and design which they often manifest in their actions are not the workings of their own minds. The intelligence and design belong to Him who impressed the thought upon the animal's mind and unceasingly sustains it in action. They themselves are not conscious of any thought, but only of "certain dim imperious influences" which urge them on. They are conscious of feelings and desires and impulses. We could not conceive of the existence of these affections in animals without their having an immediate knowledge of them. Even "the function of voluntary motion," says Hamilton, "which is a function of the animal soul in the Peripatetic doctrine, ought not, as is generally done, to be excluded from the phenomena of consciousness and mind." The conscious life of the irrational tribes seems, then, to be a life almost wholly within the senses. They have nothing of that higher conscious personality which belongs to man and is an attribute of a free intellect.

A general statement of the points made out in the foregoing inquiry will more clearly show our conception of the nature and limitations of instinct. First, we limited the word instinct so as to exclude all those automatic and mechanical actions concerned in the simple functions of organic life,—as also to exclude the operations of the passions and appetites, since these seek no other end than their own gratification. Then it was shown that instinct exists prior to all experience or memory; that it comes to an instant or speedy perfection, and is not capable of any improvement or cultivation; that its objects are precise and limited; that within its proper sphere it often appears as the highest wisdom, but beyond this is only foolishness; that it uses complex and laborious means to provide for the future, without any prescience of it; that it performs important and rational operations which the animal neither intends nor knows anything about; that it is permanent for each species, and is transmitted as an hereditary gift of Nature; and that the few variations in its action result from the development of provisional faculties, or from blind imitation. We were led to conclude that instinct is not a free and conscious possession of the animal itself. We found some points of resemblance between intelligence in man and instinct in other animals,—but at the same time points of dissimilarity, such as to make the two principles appear radically unlike.

This brief summary presents nearly all that we can satisfactorily make out respecting instinct; and at the same time it shows how much is still wanting to a complete solution of all the questions which it involves. And then there are higher mysteries connected with the subject, which we do not attempt to penetrate,—mysteries in regard to the creation and the maintenance of instinctive action: whether it be the result of particular external conditions acting on the organization of animals, or whether, as Sir Isaac Newton thought, the Deity himself is virtually the active and present moving principle in them;—and mysteries, too, about the future of the brute world: whether, as Southey wrote,

 
"There is another world
For all that live and move,—a better world."
 

If we ever find a path which seems about to lead us up to these mysteries, it speedily closes against us, and leaves us without any rational hope of attaining their solution.