We have now shown that the very forces which give vent to the attributes of man, are correlated to the physical forces. Let us now consider his attributes as manifested by his mental powers. There is no doubt the difference between the mental faculties of the ape and that of the lowest savage, who cannot express any number higher than four and who uses hardly any abstract terms for common objects or for the affections,[52] is still very great and would still be great, says Darwin, "even if one of the higher apes had been improved or civilized as much as a dog has been in comparison with its parent form, the wolf or jackal." But when we examine the interval of mental power between one of the lowest fishes, as a lamprey or a lancelet, and one of the higher apes, and recognize the fact that this interval is filled up by numberless gradations, it does not become so difficult to understand the interval between an ape and man, which is not by far so great. As in finding out what is peculiar to a living body in distinction to a body not living, we found it absurd to take man as the perfection of the animal scale—the microscopic monad possessing life as well as him—so in the case of man's mental attributes, which have always been increasing, always perfecting, since the first genuine man came into existence, it would be equally absurd to compare the intellectual man of to-day with an ape to see what attributes he possesses which the ape does not possess; but if we go down in the scale and compare the savage with the ape, the difficulty is not by far so great. It will be found on close examination, though, that man and the higher animals, especially the primates, have many instincts in common. "All," says Darwin, "have the same senses, intuitions and sensations; similar passions, affections, and emotions; even the more complex ones, such as jealousy, suspicion, emulation, gratitude and magnanimity; they practice deceit and are revengeful; they are sometimes susceptible to ridicule and even have a sense of humor; they feel wonder and curiosity; they possess the same faculties of imitation, attention, deliberation, choice, memory, imagination, the association of ideas, and reason, though in very different degrees. The individuals of the same species graduate in intellect from absolute imbecility to high excellence; they are also liable to insanity, though far less often than in the case of man."[53] Nevertheless, in the face of these facts, many authors have insisted that man is divided by an inseparable barrier from all the lower animals in his mental faculties. It only shows the improper or imperfect consideration of the subject they have under discussion.

It may be thought at first that some of the mental attributes mentioned above are not possessed by animals. I therefore will briefly consider a few of the more complex ones. We can dismiss the consideration of such attributes as happiness, terror, suspicion, courage, timidity, jealousy, shame, and wonder, as well-known attributes. Curiosity in animals is often observed. An instance mentioned by Brehm will serve to illustrate: Brehm gives a curious account of the instinctive dread which his monkeys exhibited for snakes; but their curiosity was so great that they could not desist from occasionally satiating their horror in a most human fashion, by lifting up the lid of the box in which the snakes were kept. Imitation is also found among the action of animals, especially among monkeys, which are well known to be ridiculous mockers.

It is unnecessary to refer to the faculty of attention, as it is common to almost all animals, and the same may be said of memory as for persons or places.

One would hesitate to believe an animal possesses imagination, but such is the case. Dreaming, it will be admitted, gives us the best notion of this power. Now as dogs, cats, horses, and probably all the higher animals, even birds, have vivid dreams—this is shown by their movements and the sounds uttered—"we must admit," says Darwin, "they possess some power of imagination. There must be something special which causes dogs to howl in the night, and especially during moonlight, in that remarkable and melancholy manner, called baying. All dogs do not do so; and, according to Housyeau,[54] they do not look at the moon, but at some fixed point near the horizon. Housyeau thinks that their imaginations are disturbed by the vague outlines of the surrounding objects, and conjure up before them fantastic images; if this be so, their feelings may almost be called superstitious."

The next mental faculty is reason, which stands at the summit; but still there are few persons who will deny that animals possess some power of reasoning. A few illustrations will be all that is necessary to satisfy the inquiring mind on this point. Reugger, a most careful observer, states that when he first gave eggs to his monkey in Paraguay they smashed them, and thus lost much of their contents; afterward they gently hit one end against some hard body, and picked off the bits of shell with their fingers. After cutting themselves once with any sharp tool, they would not touch it again, or would handle it with the greatest caution. Lumps of sugar were often given them, wrapped up in paper; and Reugger sometimes put a live wasp in the paper, so that in hastily unfolding it they got stung; after this had once happened, they afterward first held the packet to their ears to detect any movement within.

The following cases relating to dogs are described by Darwin: Mr. Colquhoun winged two wild ducks, which fell on the farther side of a stream; his retriever tried to bring over both at once, but could not succeed; she then, though never before known to ruffle a feather, deliberately killed one, brought over the other, and returned for the dead bird. Colonel Hutchinson relates that two partridges were shot at once—one being killed, the other wounded; the latter ran away, and was caught by the retriever, who, on her return, came across the dead bird; "she stopped, evidently greatly puzzled, and after one or two trials, finding she could not take it up without permitting the escape of the winged bird, she considered a moment, then deliberately murdered it by giving it a severe crunch, and afterward brought away both together. This was the only known instance of her ever having wilfully injured any game. Here we have reason, though not quite perfect; for the retriever might have brought the wounded bird first, and then returned for the dead one, as in the case of the two wild ducks. I give the above cases as resting on the evidence of two independent witnesses; and because in both instances the retrievers, after deliberation, broke through a habit which was inherited by them (that of not killing the game retrieved), and because they show how strong their reasoning faculty must have been to overcome a fixed habit."[55]

It has often been said that no animal uses any tool, but this can be so easily refuted on reflection, that it is hardly worth while considering; for illustration, though, the chimpanzee in a state of nature cracks nuts with a stone; Darwin saw a young orang put a stick in a crevice, slip his hand to the other end, and use it in a proper manner as a lever. The baboons in Abyssinia descend in troops from the mountains to plunder fields, and when they meet troops of another species a fight ensues. They commence by rolling great stones at their enemies, as they often do when attacked with fire-arms.

The Duke of Argyll remarks that the fashioning of an implement for a special purpose is absolutely peculiar to man; and he considers this forms an immeasurable gulf between him and the brutes. "This is no doubt," says Darwin, "a very important distinction; but there appears to me much truth in Sir J. Lubbock's suggestion,[56] that when primeval man first used flint-stones for any purpose, he would have accidentally splintered them, and would then have used the sharp fragments. From this step it would be a small one to break the flints on purpose, and not a very wide step to fashion them rudely. The later advance, however, may have taken long ages, if we may judge by the immense interval of time which elapsed before the men of the neolithic period took to grinding and polishing their stone tools. In breaking the flints, as Sir J. Lubbock likewise remarks, sparks would have been emitted, and in grinding them heat would have been evolved; thus the two usual methods of 'obtaining fire may have originated.' The nature of fire would have been known in many volcanic regions where lava occasionally flows through forests."

It becomes a difficult task to determine how far animals exhibit any traces of such high faculties as abstraction, general conception, self-consciousness, mental individuality. There can be no doubt, if the mental faculties of an animal can be improved, that the higher complex faculties such as abstraction and self-consciousness have developed from a combination of the simpler ones; this seems to be well illustrated in the young child, as such faculties are developed by imperceptible degrees. These high faculties are very sparingly possessed by the savage; as Buchner[57] has remarked, how little can the hard-worked wife of a degraded Australian savage, who uses very few abstract words and cannot count above four, exert her self-consciousness or reflect on the nature of her own existence. If there exist a class of people so inferior in their mental faculties as these, it is not difficult for us to understand how the educated animal who possesses memory, attention, association, and even some imagination and reason, can become capable of abstraction, &c., in an inferior degree even to the savage. It certainly cannot be doubted that an animal possesses mental individuality—as when a master returns to a dog which he has not seen for years, and the dog recognizes him at once.

One of the chief distinctions between man and animals is the faculty of language. Let us look at this for a moment. "The essential differences," says Prof. Whitney, "which separate man's means of communication in kind as well as degree from that of the other animals is that, while the latter is instinctive, the former is in all its parts arbitrary and conventional. No man can become possessed of any language without learning it; no animal (that we know of) has any expression which he learns, which is not the direct gift of nature to him." Any child of parents living in a foreign country grows up to speak the foreign speech, unless carefully guarded from doing so; or it speaks both this and the tongue of its parent with equal readiness. A child must learn to observe and distinguish before speech is possible, and every child begins to know things by their name before he begins to call them. "If it were not for the added push," says Prof. Whitney, "given by the desire of communication, the great and wonderful power of the human soul would never move in this particular direction; but when this leads the way, all the rest follows." No philologist now supposes that any language has been deliberately invented; it has been slowly and unconsciously developed by many steps.