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Some Important Issues in Philosophy |
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Background Essay: Some Forms of Realism Critical Presentative Realism A Critique and a Defense by Celestine N. Bittle, O.F.M.Cap.
INDEX:
In discussing the facts of sense-perception, we deal with ultimate experiences of the human subject, and we must distinguish closely between the facts themselves and the interpretation of these facts. The facts are registered by the senses, but the senses tell us nothing of the "nature" of these facts: it is the interpreting intellect which gives us an insight into their being. It is the duty of the philosopher to study the facts of everyday life and of science to draw the conclusions necessarily implied in them. The facts must dictate the theory which attempts to explain them; and any theory which fails to give an adequate account of all the facts of the case must be relinquished in favor of the one which does. It is assumed here that the reader has read the essay entitled Some Forms of Realism: A Critique of Representative and Presentative Realism. If not, the reader should read that essay before tackling this one; otherwise certain concepts may be misunderstood. The Problem of Secondary Qualities Rigid perceptionists and critical perceptionists agree that the primary qualities of objects (extension, shape, unity and multiplicity, rest and motion) are objectively real and are perceived as such. The difference between them centers in the problem of the secondary qualities (color, sound, odors, flavors, etc.). Rigid perceptionists contend that all primary and secondary qualities are objective and absolute in the sense that they exist "out there" in nature, independent of, and antecedent to, the act of perception; they are present and remain present in nature, even if there is no sense-organ in existence to perceive them. Critical perceptionists distinguish between the two classes of qualities and contend that the secondary qualities do not exist "out there" in nature as such, objectively and absolutely, but are subjective and relative, in the sense that they exist only in the act of sensation of the perceiver; secondary qualities, therefore, do not exist independent of, and antecedent to, the act of perception. However, the critical perceptionists maintain that these secondary qualities are not "purely" subjective and relative, because their causes, namely, the bodies and their properties, exist and through their influence produce these sensations of color, sound, etc., in the perceiver. According to critical perceptionists, then, secondary qualities are "causally" and potentially," but not "actually" and "formally," present in the bodies. When speaking of the "objectivity" or "subjectivity" of secondary qualities in the following discussion, the terms must be accepted in the meaning here designated. The controversy concerning the nature of the secondary qualities has been very keen among philosophers in modern times, especially among those in the classical realistic tradition (Aristotelians, Scholastics, Thomists, Contextual Realists). This is due mainly to the findings of science. Scientists in general favor the subjectivity of these qualities, as will be seen by consulting the standard works of psychology, physics, physiological psychology, and experimental psychology. The older medieval scholastics considered all qualities as formally present in the objects themselves. Redness, for instance, is a physical accident of the rose itself, independent of light; sugar is sweet in itself; ice is cold in itself; a bell really emits a sound. Others distinguished between "formal" and "fundamental" qualities. According to them, color and sound as such (and all the other secondary qualities) are not present in the object itself, but in the medium which intervenes between the object and the sense-organ; light is colored and air is sounding. This view places color and other qualities fundamentally in the objects and formally in the medium; but as such they are objective and absolute, independent of, and antecedent to, the perceiver. Among the older prominent scholastics who favored this theory are Albert the Great (Albertus Magnus), Thomas Aquinas, and Suarez. Neo-scholastics, generally speaking, seem to lean toward that form of rigid perceptionism which distinguishes between "formal" and "fundamental" qualities. This group includes J. Urraburu, Peter Coffey, and Jacques Maritain. Other neo-scholastics are critical perceptionists. Many modern-day Aristotelians and all Contextual Realists are also critical perceptionists. They claim that the secondary qualities have only a subjective existence in the perceiver, so that their formal being is dependent on the act of perception; as such, them, they exist neither in the objects nor in the intervening medium. The chemico-physical properties of things, however, are the cause of their production, in as much as the energies of objects influence the sense-organs effectively and through their stimuli produce therein the sensation of color, sound, etc. Among those who defend this view are D. Card. Mercier, John Wild, Mortimer Adler, and Jonathan Dolhenty. Critical presentative realists maintain that the facts clearly show the secondary qualities to be subjective in character; i.e., they are not independent of, and antecedent to, the act of sensation, otherwise contradictory attributes will have to be predicated of the same object in the same respect. In support of their view, they appeal to experience and science. Touch, Taste, Smell, and Hearing Touch "Heat" and "cold" are secondary qualities and, to all appearances, are objectively present in the things which come in contact with our body. But temperature is relative to the perceiver. If man's body temperature be taken as "physiological zero," any object of the same temperature will evoke no thermal experience; but anything below this zero will appear cold and anything above it will appear warm or hot. As the body temperature is heightened or lowered, objects will change from hot to cold and vice versa, although nothing was done to change their temperature. Thermal impressions also depend upon humidity. Evaporation from the skin gives the impression of coolness; but if the surrounding air is humid, so that evaporation is impeded, we have the sensation of increased heat, although the temperature is the same. Increased temperature of the air increases its capacity to absorb moisture; hence, even though the temperature of the air is increased, we experience the sensation of greater coolness. Similarly, agitation of the air around the body, for instance, by means of a fan, produces the sensation of coolness, although the temperature of the air has not been changed. If we place the right hand in a vessel of water of plus 60 degrees and the left hand in a vessel of water of plus 100 degrees and then place both hands in water of plus 80 degrees, the same water will appear warm to the right hand and cool to the left. According to science, the sensation of heat is due to electromagnetic radiation. The closer we move to its source, the hotter the objects seems to become; and the farther away we move, the less we experience of its heat. If heat were really objective, in the object itself or in the intervening medium, then the space between the sun and the earth should be filled with "objective heat"; and this heat should be more intense above the earth in the direction of the sun. This, however, is not the case: the temperature decreases as the altitude increases, and interstellar space, according to science, is many degrees below zero. From this we must conclude that the experience of heat is a subjective reaction of our nervous system. Taste and Smell All people are aware that taste is a capricious sense and that "there is no accounting for tastes." Taste and smell are physiologically closely related, and many experiences which we attribute to taste are really due to the sense of smell; the confusion is remarkable. The same substance may produce a different taste, depending on what part of the tongue it is placed. Passing from the tip to the base of the tongue, the following changes of quality have been shown by experimentation to take place:
Distilled water, after a solution of hydrochloric or sulfuric acid, tastes sweet. A weak solution of quinine sulfate, after sulfuric acid, tastes sweet at the tip of the tongue and bitter at the base. Objects, however, cannot be objectively sweet and bitter at the same time or change objectively, because of their mere position on the tongue. It is a common experience that certain substances are delicious to the taste or smell of some persons and nauseating to the taste or smell of others. If flavors and odors were objective qualities, all who can taste or smell should perceive the same objective qualities. The qualities certainly do not change objectively in themselves, simply because different persons perceive them. Men and animals perceive entirely different flavors and odors in the same object. If they taste the same objective flavors and smell the same objective odors, there should be no difference in their reactions. There is, however, a great difference, and this can be adequately explained only on the supposition that flavors and odors are not objective qualities of the objects themselves, but are chemical properties which produce effects according to the subjective character of the perceiving organs. Hearing Sound is also supposed to be objective, independent of the organ of hearing. A bell, for instance, emits a sound which corresponds to the note "c" on the scale. No matter how often we strike the bell, the note will always be the same. Let it be assumed that a bell is clanging away at a railway crossing and that its note is "c." Here, then, there is nothing to alter the note; the bell continuously emits "c." and anyone standing near by hears this identical note as long as the bell rings. However, every person in a rapidly moving train will hear the pitch of the bell rise as they near the bell, and they will hear it sink as they move away; it is only in the immediate vicinity of the bell that they hear the note as "c." Everyone in the train, from the engine to the last car, hears a different tone, ranging, for instance, from "c" to "e" and from "c" to "a" at the same moment of time, although nothing has happened to the bell to change its tone. If the "objective" tone of the bell is "c," it should be physically impossible to hear a different tone, otherwise people would hear tones which are not present and not hear the one "objective" tone which is present. That, however, is actually what is experienced; each person hears a different supposedly "objective" tone. Consequently, sound is not objectively present in the bell; to maintain its objective character involves the contradictory property of "c" and "not-c" at the same time. Due to this characteristic of sound, many classical realists place sound, not in the object itself, but in the air or intervening medium. This, however, will not save their position of rigid perceptionism. Persons standing within range of the stationary bell at any point will hear only "c." Let us suppose that the middle of the moving train is directly opposite the bell. Then every person standing near the tracks at the head of the train or at the end of the train will hear only "c," but every person within the moving train will hear a different tone, as explained above. If, then, the "objective" tone in the air is "c," this tone must be the same wherever the sound happens to travel, and everyone must hear this tone "c" and no other. That, however, is not the case; the tone is experienced as different by different persons. Consequently, formal sound is neither in the object nor in the air, but in the organ of hearing itself; in nature there are only vibrations of definite length and frequency which are then translated into sound by the individual ears in the act of sensation. Nothing seems more obvious to us than that things are really colored and that color exists in the bodies themselves. This, however, is a matter of judgment, not of sense; the eyes merely report the facts of sight and tell us nothing about the actual reality of what they perceive. If a thorough scientific investigation of the data confirms the theory of objectivity, we must, of course, accept the verdict of science; we must, however, also accept its verdict, if it can show that colors are not objective. This, critical perceptionists claim, science does. Refraction produces results which are extremely difficult to comprehend and explain, if color is objectively present in objects. The phenomena of the rising and setting sun are familiar to everyone. The sun appears much larger than usual; it appears elliptical in shape; it appears as a deep-red or golden ball; it appears to become smaller in size as the morning progresses and larger as it sinks toward the horizon in the evening. We know that none of these things are actually so. The actual sun does not change in size, shape, and color from hour to hour during the day, but remains the same throughout the year. Were the sun "objectively" red, why do we see it as white during the greater part of the day? Were it white, why do we see it as red in the morning and evening? Were either of the colors objective, we should see nothing but that one color all the time. Since the color changes continually in the unchanging sun, neither can be objective. This becomes even more obvious when we consider that people on different parts of the earth in the east and west, looking at the sun at the same instant of time, receive entirely different impressions regarding its size, shape, and color: it is big and little, read and white, round and flattened, at the selfsame moment. But this is obviously impossible; the real sun cannot have such opposite qualities at one and the same moment. At sunrise the real sun is still actually below the horizon, although we "see" a red sun in the eastern portion of the sky. The sun, therefore, is not there at all where we see it. This phenomenon is due to the refraction of the sun's rays. What we actually see, then, is not the sun as an object; it is a consciously apprehended retinal image, produced by the radiant energy of the sun in the organ of sight, and that is subjective. The stars in the heavens present a somewhat similar phenomenon. The stars, even those which are called "fixed," move at tremendous speeds. We cannot see a star until the light rays emitted by it reach the eye. Light travels at a velocity of over 186,000 miles per second; despite this speed, many stars are so distant that it takes hundreds and thousands of years for their light to reach the earth. Let us assume that a certain star is a thousand light-years away and that it travels in the general direction of west to east at a rate of 1,000,000 miles a year. At the moment, then, when we look at this star, we see it where it was located one thousand years ago; this means, that we see it one billion miles to the west of where it is at present. The star is not there where we see it, and where it actually is we do not see it at all. And this is true of all the so-called fixed stars. We even see the sun only where it was eight minutes ago. It follows, then, that we never see the stars themselves as real objects in the heavens, because they are never visible as such where they actually stand. Then what do we perceive? Evidently, a consciously apprehended retinal image. Rainbows are also phenomena which show that colors are not in the objects, contrary to the seemingly evident testimony of our eyes. The colors of a rainbow seem as objectively real in the mist or in the rain as the colors of glowers or of other objects. Yet the water drops in which the rainbow is seen to exist are colorless. It is all a matter of the refraction and reflection of light rays. That the water drops are in no way actually colored by the light rays, is obvious from the fact that persons not standing at the proper angle will see no rainbow. A dozen persons may view a spray of water, but only a few, those who stand in the right relation to the sun and spray, will see the colors; all others will see only a colorless spray. If the colors were objectively present, independent of, and antecedent to, the perceivers, all should be able to see the colored water. The water drops are thus observed to be colored and not colored at the same time, if rigid perceptionism were correct. The same is true of mirages and of the iridescence seen in oil films, soap bubbles, sea shells, and in the feathers of many birds. Aristotle and many of the older scholastics knew these facts and on their account made the distinction between "real" and "apparent" colors. The phenomena of the rising and setting sun and of the distant stars show that we do not perceive these objects themselves in any form of direct perception; and the rainbows and similar phenomena show that their colors are not in the objects. The images of these things, then, can only be retinal images; and they are subjective. Nor can we say that the colors are in the air or ether occupying the space between the object and the eye. Air and ether are colorless in this intervening space. If we stand at right angles to the colored object and gaze straight through the intervening space, we perceive no color traveling from the object to the eye. Where, then, is formal color? Solely in the perceiving organ. There is no "objective" white color in sunlight, although we perceive it frequently. The seven prismatic colors of sunlight, striking the same retinal points of the eye, produce the sensation of white, although there is no "white" in the spectrum. In fact, all complementary colors do this, as red and green and green-blue, orange and blue, gold and blue, yellow and indigo-blue, green-yellow and violet. The law of color mixture reads: "For every long wave of the visible spectrum (that is, for every wave not shorter than 563.6 millimicra) a definite short wave can be found so that when the two waves are mixed in appropriate proportions, each component of the mixture will neutralize the chromatic effect of the other and the sensation of neutral white will arise; but if the relative strength of the two components is not appropriately adjusted, the neutralization of one component is incomplete and the result of such a mixture is the sensation of an unsaturated color whose tone is determined by that of the stronger component." This law is proved experimentally by means of the color top or color disk revolving at rapid speed. The disk or top still retains its original colors; but as the speed is increased the eye perceives a neutral gray. If I take one disk with 170 degrees yellow and 190 degrees indigo and another disk with 300 degrees black and 60 degrees white and revolve them with sufficient speed, both disks will look exactly alike in color. The eye sees the same color, though the disks and their colors have not changed. As it is, the eye sees a color which is not there and does not perceive the colors which are there. Snow, steam, foam, and clouds appear as white, but they all consist of colorless water particles. The mass of their surfaces simply reflect all the colors of sunlight to the eye, and the sensation of "white" is produced on the retina. The contrast box makes colors appear very different to the eye than they (supposedly) are in reality. A colored background is seen through a compartment, and the latter is illuminated with different intensities of filtered lights. Without changing the background in any way, so that its "objective" color remains the same, yellow can be made to look like an orange-red or green; bluish-green, like a slightly greenish black; white, like a purplish red or a bluish green or a blue or a gold or even a black. We have here a case of the same color appearing to the eye as a different color, and each individual color can, under controlled conditions, be made to look like practically every other color. If blue and yellow dry powders are mixed, the mixture appears as green to the eye, although this gross mixture does not change the original colors in any way. That the powders are still blue and yellow, can be shown by looking at the mixture through a powerful magnifying glass; the blue and yellow particles will be seen to lie in juxtaposition. Where, then, is the green color? Not in the objects, for they remain blue and yellow. Printers make use of this principle in three-color printing; red, blue, and yellow, by means of a mere superposition and juxtaposition of colored particles, give the impression of all colors, although there are no intermediate colors present. The light rays, striking the same retinal elements, produce therein a sensation of colors which are blends of the original color particles. Filtered light shows the same effect. Take two pieces of glass, one blue and one yellow, and hold them in such a way that they overlap, but with a space between them. You, looking at the overlapped pieces, see them now as green; but others, viewing them from the side, still see them as blue and yellow. The "objective" color cannot be blue and yellow and also green at the same time. There is no green in the glass, because the glass did not change; still, that is what you observe. Due to the difference in position, the same objects produce the impression of different colors in the eyes of the observers. And so it is with all other colors. If color were "objective," independent of, and antecedent to, the act of perception, we are forced to state that this objective color is "green" and "not-green," "blue and yellow" and "not-blue and not-yellow" at the same time. Stereoscopic color vision shows plainly that the blending of colors takes place in the organ of perception. Fasten a piece of bright blue paper over the one picture of a stereoscope and a bright yellow paper over the other; adjust the distance to the eyes in such a manner that only blue light reaches the one eye and yellow light the other eye. Here, then, we have no blending of colors in the object and no blending of light rays between the papers and the eyes. Gazing fixedly and with equal intensity at both pieces of paper (provided both eyes are practically normal in visual strength), the perception of green will gradually appear. This is due to the chiasma, or crossing, of the optic nerve bundles of both eyes to the optic centers in the two hemispheres of the brain. This is an instance of psychological color mixing, and it may be considered a crucial experiment; the new color, green, is neither a blend in the object, nor in the intervening medium, nor in the single eyes, but is an effect produced by the light rays in the entire perceptive organ of sight, and it is subjective in character. Since the same principle applies to other colors, color as such cannot be objective. To Part Two of Critical Presentative Realism: A Critique and a Defense Enrich Your Life With a Philosophy Book...
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