of judgment, not of immediate direct perception, not in fact of perception at all. All that we properly perceive in such a case, all that we are directly conscious of is the fragrance or the sound. That these are produced by the rose and the bell is not perceived, but only conceived, inferred—known, if at all, only by the aid of previous experience.
Sensation as distinguished from Perception.—According to the view now presented, sensation, as distinguished from perception, is the simple feeling which results from a certain affection of the organism. It is known to us merely as feeling. Perception takes cognizance of the feeling as an affection of the organism, and also of the organism as thus affected, and consequently as external to the me, extended, having parts, etc. It apprehends also objects external to the organism itself limiting and affecting its movements. Sensation is the indispensable condition of perception. If there were no sensation, there would be no perception. The one does not precede, however, and the other follow in order of time, but the one being given, the other is given along with it. The two do not, however, coexist in equal strength, but in the relation, as stated by Hamilton, of inverse ratio; that is, beyond a certain point, the stronger the sensation, the weaker the perception, and vice versâ.
Sensation as an Affection of the Mind.—It has been common to speak of sensation as lying wholly in the mind. Primarily, however, it is an affection of the nervous organism, and through that organism, as thus affected, an impression is made on the mind. If it were not for the mind present with the organism, and susceptible of impression from it, and thus cognizant of changes in it, the same changes might be produced in the organism as now, but we should be entirely unconscious of and insensible to them. In certain states of the system this actually happens, as in sound sleep, the magnetic state, the state produced by certain medicinal agents as ether, chloroform, opium, and the intoxicating drugs of the East. In those cases, the connection between the mind and the nervous organism seems to be in some manner interrupted or suspended, and consequently there is for the time no sensation. The nerves may be irritated, divided even, and still no pain is felt.
It is not true, however, that the sensation is wholly in the mind. It is in the living animated organism, as pervaded by the mind or spiritual principle, mysteriously present in every part of that organism, and cognizant of its changes; and neither the body alone, nor the mind alone, can be said to possess this faculty, but the two united in that complex mysterious unity which constitutes our present being.
§ III.—Analysis and Classification of the Qualities of Bodies.
Difference of Qualities.—The qualities of bodies as known to us through sensation and perception are many and various. On examination, a difference strikes us as existing among these qualities, which admits of being made the basis of classification. Some of them are qualities which strike us at once as essential to the very existence of matter, at least in our notion of it, so that we cannot in thought divest it of these qualities, and still retain our conception of matter. Others are not of this nature. Extension, divisibility, size, figure, situation, and some others, are of the former class. If matter exists at all, it must, according to our own conceptions, possess these qualities. We cannot think them away from it, and leave matter still existing. But we can conceive of matter as destitute of color, flavor, savor, heat, cold, weight, sound, hardness, etc. These are contingent and accidental properties not necessary to its existence.
How named and distinguished.—Philosophers have called the former class primary, the latter secondary qualities. The former are known à priori, the latter by experience. The former are known as qualities, in themselves, the latter only through the affections of our senses.
The primary qualities then have these characteristics:
1. They are essential to the very existence of matter, at least in our conception.
2. They are to be known à priori.
3. They are known as such, or in themselves.
The secondary, on the contrary, are:
1. Accidental, not essential to the notion of matter.
2. To be known only by experience.
3. To be learned only through the affection of the senses.
Further Division of secondary Qualities.—A further division, however, is capable of being made. The secondary qualities, as now defined, comprise, in reality, two classes. There are some, which, while known to us only through the senses, have still an existence as qualities of external objects, independent of our senses. As such they are objects of direct perception. Others, again, are known, not as qualities of bodies, but only as affections of sense, not as objective, but only as subjective, not as perceptions, but only as sensations. Thus I distinguish the smell, the taste, and the color of an orange. What I distinguish, however, is after all only certain sensations, certain affections of my own organism. What may be the peculiar properties or qualities in the object itself which are the exciting cause of these sensations in me, I know not. My perception does not extend to them at all. It is quite otherwise with the qualities of weight, hardness, compressibility, fluidity, elasticity, and others of that class. They are objects of perception, and not of sensation merely.
These Classes, how distinguished.—The class first named, are qualities of bodies as related to other bodies. The other class are qualities of bodies as related only to our nervous organization. The former all relate to bodies as occupying and moving in space, and come under the category of resistance. The latter relate to bodies only as capable of producing certain sensations in us. We may call the former mechanical, the latter physiological.
Connection of Sensation with the external Object.—From long habit of connecting the sensation with the external body which produces it, we find it difficult to persuade ourselves that taste and smell are mere affections of our senses, or that color is really and simply an affection of the optic nerve of the beholder, and that what is actually perceived in these instances is not properly a quality of the external object. A little reflection, however, will convince us that all which comes to our knowledge in these cases, all that we are properly cognizant of, is the affection of our own nervous organism, and that whatever may be the nature of the qualities in the object which are the producing cause of these sensations in us, they are to us occult and wholly unknown.
Power of producing these Sensations.—It is not to be denied, of course, that there is in external objects the power of producing these sensations in us, under given circumstances; but to what that power is owing, in what peculiarity of constitution or condition it consists, we know not. We have but one name, moreover, for the power of producing, and the effect produced. Thus the color, taste, smell, etc., of an object may denote either the sensation in us, or the unknown property of matter by virtue of which the sensation is awakened. It is only in the sense last mentioned, that the qualities under consideration may properly be called qualities of bodies.
Enumeration of the several Qualities as now classed.—According to the classification now made, the qualities of bodies may be thus enumerated.
I. Primary.—Extension, divisibility, size, density, figure, absolute incompressibility, mobility, situation.
II. Secondary.—A. Objective, or mechanical—as heavy or light, hard or soft, firm or fluid, rough or smooth, compressible or incompressible, resilient or irresilient, and any other qualities of this general nature resulting from attraction, repulsion, etc.
B. Subjective or physiological—as color, sound, flavor, savor, temperature, tactual sensation, and certain other affections of the senses of this nature.
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