LITMIR.BIZ

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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.

      § IV.—Organs of Sense.—Analysis of their Several Functions

      Number of the Senses.—The different senses are usually reckoned as five in number. They may all be regarded, however, as modifications of one general sense, that of touch—or, in other words, the susceptibility of the nervous system to be excited by foreign substances brought into contact with it. This is the essential condition of sensation in any case, and the several senses, so called, are but so many variations in the mode of manifesting this excitability. There is a reason, nevertheless, for assigning five of these modifications and no more, and that is, that the anatomical structure indicates either a distinct organ, as the ear, the eye, etc., or at least a distinct branch of the nervous apparatus, as in the case of smell and taste, while the whole nervous expansion as spread out over the surface of the body contributes to the general sense of touch.

      The Senses related to each other.—Distinct Office of each.—It is evident enough that these several senses sustain a certain relation to each other. They are so many and no more, not merely by accident; not merely because so many could find room in the bodily organization; not merely because it might be convenient to have so many. Let us look at the office performed by each, and we shall see that while each has its distinct function, not interchangeable with that of any other, it is a function more or less necessary to the animal economy. Remembering that the design and use of the several senses is to put us in possession of data, by means of which, directly or indirectly, we may gain correct knowledge of the external world, let us suppose the inquiry to be raised, What senses ought man to have for this purpose? What does he need, the material universe remaining what it is?

      Function of the Sense of Touch.—Things exist about us in space, having certain properties and relations. We need a sense then, first and chiefly, that shall acquaint us with objects thus existing, taking cognizance of what lies immediately about us in space. This we have in the general sense of touch, making us acquainted with certain objective or mechanical qualities of external objects.

      This Sense, how limited.—This, however, avails only for objects within a short distance, and capable of being brought into contact. It operates also synthetically and slowly, part after part of the object being given as we are brought into contact with different portions of it successively until the process is so far complete that, from the ensemble of these different parts, our understanding can construct the whole.

      Possibility of a Sense that shall meet these Limitations.—We can conceive of a sense that should differ in both these respects—that should take cognizance of distant objects, not capable perhaps of being brought into contact—and that should also operate analytically, or work from a given whole to the parts, and not from the parts to a whole, thus giving us possession at once of a complete object or series of objects. Such a sense, it is easy to see, would possess decided advantages, and in connection with the one already considered, would seem to bring within the sphere of our cognizance almost the complete range of external nature. This we have, and this exactly, in the sense of vision. It takes in objects at a distance, and takes in the whole at a glance.

      This new Sense still limited.—This new sense, however convenient and useful as it is, has evidently its limitations. It is available only through a given medium, the light. Strictly speaking, it is the light only that we see, and not the distant object; that is known indirectly by means of the light that variously modified, travels from it to the eye. When this fails, as it does during several hours of the twenty-four, or when it is intercepted by objects coming between and shutting out the forms on which the eye seeks in vain to rest, then our knowledge from this source is cut off.

      Still another Sense desirable.—Under these circumstances, might it not be well, were there given an additional sense, of the same general nature and design, but operating through a different medium, sure to be present wherever animal life exists, so that even in the darkness of the night, or the gloom of the dungeon, we might still have means of knowing something of the surrounding objects. And what of this medium, or avenue of sense, were of such a nature as to be capable of modification, and control, to some extent, on our part, and at our pleasure,

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