The understanding of compound, antecedent to that of acquired, perception

CHAPTER XXXIX.

COMPOUND AND ACQUIRED PERCEPTION.

1. A SATISFACTORY understanding of acquired perception will be promoted if we notice, and distinguish from it, a form of cognition closely related to it, and which also should be considered for its own sake. We refer to that act of the intellect whereby the immediate perceptions of the same object by two or more different senses are combined into one perception, which combination is itself an act of intuitive and concomitant cognition.

This compounded perception differs from acquired perception, because there is no inference in it; the knowledge which it yields is presentationally given; but it is related to acquired perception, because it is the source whence the constructions of thought and the rules of inference employed in acquired perception are originally obtained.

These remarks may be illustrated from the experience of a boy born blind, whose eye was couched for cataract by an English surgeon. After he had somewhat gained the use of his sight, he could not call the cat and the dog by their right names, or tell which was the cat and which the dog. But, being easily able to recognize each by the sense of feeling, he caught the cat one day, and, shutting his eyes, passed his hands over her, so as to ascertain which animal he had been seeing. Then, setting her down, he said, "So, puss, I shall know you another time."

In this case two cognitions of the same object were intuitive and independent of one another, and their union resulted from an identification, also intuitive, of the object of the one with the object of the other; for the cat, as seen and as felt, presented relations of place and movement, of causation and simultaneity, which could not belong to two objects. The whole perception of the cat as an object with certain visible and certain tactual marks was an intuitive, though a compound, act of cognition.

At the same time it is evident that this immediate cognition prepared the mind making it for another perception in which a mere exercise of sight would enable the boy to supply the tactual character of the object, or in which the mere handling of

the animal would enable him to ascribe to it a certain visible appearance; and either of these perceptions would be properly an acquired one. In like manner, should one perceive quicksilver to be a heavy fluid by dipping his hand in it, his identification of the quicksilver as seen with the quicksilver as felt would be intuitive; and this would be the basis of an inferential perception from sight alone of the heavy fluidity of that metal. Compound perception being thus a condition of acquired perception, a consideration of the former is our best introduction to a consideration of the latter.

First, then, we remark that compound perception is the beginning of any adequate knowledge of things external. Till we unite into one whole the partial cognitions of a thing presented by the different senses, we can scarcely be said to have any comprehension of an external object.

But things internal, which are the objects of consciousness, cannot be said to be known by a composition of perceptions, inasmuch as they are perceived by a cognition which is complex, but which is not compounded of cognitions from different sources.

Again, let us note that compound, in separation from acquired, perception is adequate for the complete cognition of comparatively few objects, and, like the more simple intuitions of which it is composed, is more easily illustrated by examples that are not wholly intuitional than by those which exhibit its own workings only. The latter are mostly of a subtile character, and are not matters of ordinary observation. This mode of procedure will not be objectionable provided the illustration, in its essential feature, shows a composition of intuitions. My perception of the apple which I hold in my hand may not be purely presentational. Nevertheless, the eye immediately perceives it as a circular colored object, in a certain direction from the centre of vision; the hand recognizes a round smooth object, of a certain weight and hardness; while the nose discerns it as an odoriferous, and the tongue as a sapid, substance. Moreover, the peculiar taste is experienced only when the object held in the hand touches the tongue; the odor becomes faint and is lost when it is removed from the nostrils; and when the hand moves hither and thither, the apple correspondingly changes its place and direction in the field of vision. These things are perceived intuitively; and in connection with them we learn, by intuition, that the object held in the hand, that which we see, that which we feel, that which we smell, and that which we taste, are all one and the same. But other particulars about this apple-for example, its solidity and its distance from the eye- may not be intuitively known.

312

The determi

own body.

The purest exercise of compound perception, and nate knowl- the most important, takes place when the infantile edge of one's mind first forms definite conceptions of the members of his own body, and of the body as a whole. This, doubtless, is a gradual accomplishment, and results principally from an attentive exercise of the senses of touch and sight, in connection with muscular and organic feelings. The latter present the body and each of its parts as extended, as solid, and as possessed of physical power; they give also an indistinct notion of the location of the parts with reference to one another. Then touch and sight give definiteness to the rudimental perceptions of internal feeling. Of the two, touch may be considered to operate first. When one little hand grasps in succession the fingers and the thumb, the palm and the wrist, of the other, the boundaries of each member and its size become definitely known. In the same way the features of the face and other parts of the body are touched and bounded. greatly assisted by sight. While touch slowly traverses the But this determination is surface of a limb, sight perceives it all at once; and the eye easily combines into one exact conception the explorations of the hand. In doing so, the superficial extent of portions of the body as ascertained by feeling, being immediately identified with the same as seen, any limb furnishes a standard for the measurement of the whole body. For this reason the estimation of size and distance by sight, even as regards one's own body, is only partially intuitive.

The cogni

In this connection let us notice an interesting distion of the cussion respecting our perception of externality. The extra-organic externality of the different parts of the body, one to purely intui- another, is immediately given in connection with mustional. cular and organic sensations, and becomes more apparent as these sensations receive attention. This perception is greatly strengthened when the hand touches different parts of the body. Then two definitely bounded parts of the body are each immediately recognized as sentient and as solid, and as external to one another.

But the question has been raised whether any non-organic substance can be immediately known as external to the body, save by a deduction consequent upon the perception of the mutual externality of the parts of the organism itself.

It has been held that without this perception, as an antecedent condition, all external objects would be recognized only as affections of the mind. This position is an extreme one. Hamilton suggests a simpler theory when he says: istence of an extra-organic world is apprehended

66 The ex

. . in the

consciousness that our locomotive energy is resisted, and not resisted by aught in our organism itself." In other words, we perceive, at the surface of the body or of some limb, a power pressing upon us, or resisting our pressure, which power we know not to be exercised by ourselves or within our body.

But power is perceived only as possessed and exercised by a substance; therefore, when we say that we perceive an external power, this only partially expresses the fact that a substance is perceived exercising the power.

It may be allowed that this perception of the external agent is inferential, and is based on the knowledge of physical causes obtained from our bodily life, and especially from our own muscular efforts; in other words, that we infer an external cause of motion similar to those we have observed within. But this ground of inference may be easily distinguished from a knowledge of the parts of the body as external to one another. We therefore think that the external substance can be perceived without reference to the mutual externality of the parts of the body.

At the same time it is clear that this last-mentioned knowledge greatly contributes to render definite our perception of things external, and enables us to determine their character as we could not otherwise. When one hand is laid on the other, each not only distinguishes the other from itself, but also feels the pressure or the resistance of the other. But when an extraorganic substance presses either hand, the sensation is in the hand alone. This contrast brings into relief the externality of

the extraneous substance.

objects in

with our

The solidity Moreover, comparing the object as felt with the of external body as felt, we determine its solidity, size, and shape ferred from by the employment of rules obtained in the examinacomparison tion of our own limbs. This process, as regards bodies. solidity, or the space-filling property of matter, is well described by President Porter. When a blind man," he says, "grasps his own arm or wrist, he knows certain muscular sensations as extended through, and posited in, the space within the opposite surfaces that he touches. If his wrist is withdrawn from the enclosing grasp, and an extra-corporeal object is inserted in its place, the adjustments of the grasping hand are the same as before; the dim knowledge of the space which these adjustments involve is also the same. . . . The wrist is known by direct perception as space-filling; the enclosing hand is a measure of the space enclosed. The same enclosing or grasping hand measures the surface of another body; but this body yields no muscular percepts involving extension. It occupies, however, precisely the space which the other filled. It is known,

therefore, as space-filling, and as filling other space than that of the body."

This quotation sets forth the original perception of external solidity; the figure and size, direction and distance, of external objects are first perceived in a similar way. Indeed, all man's knowledge of the universe originates from cognitions respecting his own body.

Acquired perception

2. In discussing compound perception, we have insensibly entered upon the consideration of that mode defied and of cognition for which this perception is the preparaillustrated. tory basis. Compound and acquired perception are

so related that they are commonly discussed together as forming but one process. We have preferred to distinguish them, the latter being inference from past experience, and the former the composition of intuitions, or presentations.

We have now to remark that not every kind of inference from sense-cognitions can be called acquired perception.

In the first place, no inferred knowledge can claim this title unless it result from some impression which the object of it, the thing perceived, may make, more or less directly, on our nervous system, or sensorium. Hearing a clattering noise on the street, I may be said to perceive a wagon passing; but I cannot be said to perceive the driver, though I may conclude that there is some one driving, for the wagon, but not the driver, is immediately related to the noise.

In the second place, the exercise of acquired perception exIcludes all formal or doubtful inferences. The action of this power being habitual and easy, quick and absolute, it can be distinguished from immediate intuition only by philosophical scrutiny. Therefore, should one, hearing such a noise as we have mentioned, be in doubt whether it were thunder, or cannonading, or the

"Car rattling o'er the stony street,"

his conviction regarding its origin would not be a perception, but only a probable inference.

These remarks may be illustrated by the story of a traveller. When Captain Head was traversing the wild Pampas of South America, "his guide one day suddenly stopped him, and, pointing high into air, cried out, 'A lion!' Surprised at such an exclamation, accompanied by such an act, he turned up his eyes, and with difficulty perceived, at an immeasurable height, a flight of condors soaring in circles in a particular spot. Beneath this spot, far out of sight of himself or guide, lay the carcass of a horse, and over that carcass, as the guide well knew, a lion,