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sations of an electrical condition, whether they result from the employment of machines, or have a natural cause, such as the state of uneasiness which precedes a storm.
From the preceding, the writer will see how much the author excels in this naturalist method, which consists of classification and description ; but there are analyses of a more difficult order, whose object is the perception of exteriority and extension.
Touch is the most general sense; it is probable that it is not wanting in any being endowed with sensibility, and its intellectual importance is great. It gives us notions of size, form, direction, distance, and situation. Touch, considered as a source of these ideas, is not a simple sense ; it supposes, in addition, the sense of motion. Our appreciation of the weight of a body depends very much upon the exercise of the muscles, although it may result from a simple sensation of pressure exercised upon the skin. Weber shows this by an experiment. If we lay a weight of thirty-two ounces upon a motionless and supported hand, we may vary the quantity of this weight from eight to twelve ounces without the variation being perceptible to the subject of it; on the contrary, if the muscles of the hand are in action, no imperceptible variation, except between one and a half to four is possible. Whence Weber concludes that the valuation of the weight is more than doubled by the play of the muscles.
Muscular sense is no less important for the perception of extension. Properly speaking, this quality, and those of size, form, etc., which belong it, are revealed to us, as we have seen, by the movements which they cause in us; the feelings which they produce are the feelings of motion or of the condition of the muscles. What we have now to ascertain is to what point the sense of touch contributes to our fundamental notion of the exterior world ; that is to say, to extension, of which distance, direction, position, and form are only modifications.
Let an arm be moved in empty space, and see what is the result. The absence of determinate marks to limit the beginning and the end of the muscular movement leaves a certain vague character upon our sensation of motion. But if to the sense of motion we add the sense of touch, if the movement takes place, for instance, from one side of a box to the other, there we get resist
ance, and two distinct conditions, which constitute a mark in consciousness. In the same way, if we pass our hand over a surface, we feel at the same time a tactile sensation and a sensation of continued motion. It must also be remarked, that the movement of the arm in empty space not being determined by any contact, renders us incapable of distinguishing the successive from the co-existent (or time from space). Now, so long as this distinction is impossible, we cannot know extension, the foundation of which is co-existence. Time and space are two correlatives, one of which cannot be known without the other, but which are distinct the one from the other. Succession is a simple fact, co-existence is a complex fact. When the serial order of our sensations can neither be changed nor replaced, that is a succession. When it can be replaced, taken in an indifferent order, there is co-existence. Mr. Herbert Spencer is quoted on this subject by Mr. Bain as follows :
• The chain of states of consciousness, A to Z, produced by the motion of a limb, or of something over the skin, or of the eye along the outline of an object, may with equal facility be gone through from Z to A. Unlike the states of consciousness constituting our perception of sequence, which do not admit of an unresisted change in their order, those which constitute our perception of co-existence admit of their order being inverted—occur as readily in one direction as the other.'1 It is not without interest to compare this explanation with that of Kant.
The combined sensations of movement and of touch give us notions of length, of surface (extension to two dimensions), solidity (extension to three dimensions). Distance supposes two fixed points which may be recognised by a movement of the hand, the arm, or the body. Direction implies a marking point, our body is the most natural ; it serves to measure the right, the left, the back, and the front. Situation, that is to say relative position, is known if direction and distance are known. Form depends upon muscular movements, made in order to follow the outlines of a material body.
It has been more than once discussed, whether the superior
*Spencer's Psychology, p. 384. Bain.
sense is sight or touch. The two solutions may be found in Condillac. Most psychologists have declared for touch; most physiologists for sight. Mr. Bain is of opinion of the latter; we have seen that he even places touch below hearing. Without stopping at the physiological study of the sense of sight, and of the mechanism of the muscles which regulate its adaptation, let us examine three disputed questions, that of binocular vision, of reflex imagés, and of the complex perceptions of sight.
How does it happen that although the image of each object paints itself in the depth of each eye, upon each retina, the object is nevertheless perceived as simple, and not as double? This so often discussed problem has assumed a new aspect since the communication made by Wheatstone to the Royal Society on presenting his stereoscope. When we regard a distant object, says this physiologist, the two visual axes are sensibly parallel, and the images which depict themselves in each eye are similar ; in this case there is no difference between the visual appearance of an object in relief and its projection upon a plane surface. Upon this the diorama is founded. On the contrary, when the object is near, as the visual axes must converge, the images become dissimilar, and they are the more unlike as their convergence becomes greater. It is this dissimilarity, of images which is, in optics, the indicator of solidity or of the three dimensions. The greater the dissimilarity, the more clearly the third dimension is suggested. The stereoscope gives the illusion of solidity by presenting to the eye two dissimilar images ; by these means it imitates nature, and produces the same effects, while painting, which produces two similar images, cannot be confounded with solid objects. And now, if we remark that the images painted on the retina are the materials of vision, that they serve to suggest to us a mental construction, which alone constitutes sight properly so called, that there is produced in the mind, by the sight of an exterior object, an aggregate of past impressions which the impression of the moment suggests and does not constitute, we understand that it matters very little whether these materials which serve to the ulterior working of the mind be furnished by two images, as in man, or by thousands, as in insects. The difference or the resemblance of images only teaches us whether the object is distant or near.
As to that frequently offered difficulty, how images reversed upon the retina can appear straight to us--it only shows that one is completely mistaken concerning the processes proper to the sense of sight. Our ideas of high and low are due to our sense of movement, and in no way to optic images.
The complex sensations of sight result from the combination of optic effects, and the sensations of movements produced by the muscles of the globe of the eye. Here, as in the case of touch, the combination of visual perceptions and of movements is the groundwork of our perception of the exterior world. If we follow a moving light with the eye, we experience at the same time two sensations : one of light, the other of movement. The latter varies according as the right or left muscles are employed to move the eye, as a consequence of the direction of the light. The combined sensations of sight and movement give us speed, distance, succession, and co-existence. The particular movements of the muscles cause us to know the circle, angles, complex angles, surfaces, and solids. In short, all that has been stated of the combined sensations of touch and motion applies, mutatis mutandis, to the combined sensations of sight and motion.
Before ascending into the higher region of psychology, by passing from sensation to thought, we have to review in as complete a manner as possible all the phenomena which are the raw material of intelligence and of will. Such are the appetites and the instincts.
Instinct is defined as the opposite to that which is acquired by education or experience. We may say that it is an unlearnt power of accomplishing actions of every sort, particularly those which are necessary and useful to the animal. This study of the instincts, which Mr. Bain justly claims as one of the most original portions of his work, has not hitherto been the object of any important researches by psychologists. Psychologists are, indeed very incomplete upon many points. Several explanations, however, are to be found in the germ in Müller, and the author states in many instances that he has taken advantage of them.1 In our opinion the word instinct tends to produce errors. In the first place, it may be thought that it is a question of those curious phenomena proper to the lower animals, whose origin and cause still remain impenetrable ; and thus we immediately get the idea of a general and comparative psychology which shall embrace all the manifestations of mental life. This is in no wise the case. The author keeps to man, and this instinct which he is about to study may be illustrated by the clearer term instinctive movements. Taken in their entirety, they constitute a complete order of primitive dispositions, a complete primordial structure, which serves as a basis for what the human being shall become at a later stage, on the development of sentiment, of volition, and of intelligence. These instinctive acts form five groups :
1 Senses and Intellect, chap. iv.
First, Reflex actions.
Thirdly, The primitive arrangements which render harmony and combination of certain actions possible.
Fourthly, The union of feeling with its physical manifestations. Fifthly, The instinctive germ of volition.
The author treats of the two first points as a simple physiologist, and I have regretted for my part that language has been nowhere studied in his work as a psychological faculty.
What are the actions which are due to the primitive impulses of the nervous and muscular mechanism ? That is what we are about to find out. Let us first remark movements which are associated among themselves prior to all experience, and to all volition. Such is the alternate movement of a child's two legs, even before he knows how to walk. Other associated movements are simultaneous ; for example, that of the child's two arms and two eyes. It may be said that there is a general law of harmony in the whole muscular system, from whence it arises that when we look or listen attentively the body stops,
1 See Müller, Manual of Physiology, vol. i. p. 632.