THE NEXT COMMON CRITICISM OF REALIST EPISTEMOLOGY comes from the empiricists such as Locke, Berkely, and Hume. If knowledge of reality is informed by the senses, and the senses are manifestly unreliable, how can our knowledge of reality be reliable? Typically, the empiricists would point to the "bent stick" in the water, the apparent displacement that occurs as a result of parallax, or the discrepancy between those who see color and those who are color blind (who's to say colors are real, and not just something that is in the one who perceives?). A rectangular paper looks rectangular when looked at straight ahead, but it looks trapezoidal when viewed form an angled vantage point. An analogous phenomenon in the sense of hearing is the changing pitch associated with the Doppler effect. With the deviation between our senses and reality, how can we say we know reality when all our knowledge comes by and through these unreliable senses?
A variety of examples of "relativity in perception"
Parallax
Refraction
Color Blindness
The Doppler Effect
Dr. Knasas disagrees that the momentary or occasional deviation in the senses that is at the center of the "relativity in perception" critique of the empiricist school presents an insurmountable problem. "The relativity in perception is not sufficiently great to justify doubt about immediate realism." Though there may be variances in perception as a result of the relativity that is intrinsic to that perception, there is sufficient basis to be firm about the essential fact that we are perceiving something immediately real. There is sufficient information to begin philosophy.
The epistemological realism of St. Thomas did not demand perfection in the direct knowledge of real things. In attacking epistemological realism, moderns confuse the "immediate cognitional presence of the real" with "an immediate physical presence of the real." "Physical presence," Dr. Knasas insists, "demands exactitude and brooks no exception." However, the "immediate cognitional presence of the real" may not be so exact or so perfect. Often enough real objects impress themselves in our mind "at the end of long chains of physical causality," and, as a result, real things impress themselves in our cognition imperfectly. There are time, however, that the "physical presence" and the "immediate cognitional presence" of the real align perfectly.
Although Dr. Knasas did not suggest it, one should note that the "relativity in perception" can be explained by us, adjusted to by us, which is another way of saying that we can often explain how and why the "immediate cognitional presence of the real" departs from the "immediate physical presence of the real." Our ability to do this indicates that we have sufficient grasp of the reality behind the relativity that is intrinsic in perception to be able to correct for the latter. Thus we can explain why the color blind man does not see color, whereas the normal man does, and we can even invent tests to determine whether someone is color blind and whether he suffers from monochromacy, dichromacy, or trichromacy. We can explain, by understanding refraction and the effect that a change in medium has on the direction of light waves as a result of a modification of their speed, why the image of the twig in the water appears bent. We can explain why vantage point affects our perception of the shape seen. We can explain why the velocity of an object that emits sound affects the pitch of the sound. These adjustments, it would seem, would be impossible if we did not have a grasp of the underlying reality behind the relativity in perception. Moreover, the "relativity in perception" is itself part of reality, as it would not be reflective of reality if my senses did not take into consideration changes in media, in velocity, in vantage point, and so forth.
In summary, the objections of the empiricists seem rather easily overcome. They surely are not sufficient to have us jettison our common sense and advocate a total lack of correlation between the real about us, and our cognition of that real world within us, a cognition that is mediated through the sufficiently reliable senses.
[S]ufficient immediate realism exists for one to initiate his philosophizing. You do not have to know what is the exact shared of color of the poppies, the exact configuration of the paper, the exact subject of the motion. For philosophy to begin it is enough that sense cognition proves real color, shape, and motion.
The epistemological realism of St. Thomas did not demand perfection in the direct knowledge of real things. In attacking epistemological realism, moderns confuse the "immediate cognitional presence of the real" with "an immediate physical presence of the real." "Physical presence," Dr. Knasas insists, "demands exactitude and brooks no exception." However, the "immediate cognitional presence of the real" may not be so exact or so perfect. Often enough real objects impress themselves in our mind "at the end of long chains of physical causality," and, as a result, real things impress themselves in our cognition imperfectly. There are time, however, that the "physical presence" and the "immediate cognitional presence" of the real align perfectly.
Although Dr. Knasas did not suggest it, one should note that the "relativity in perception" can be explained by us, adjusted to by us, which is another way of saying that we can often explain how and why the "immediate cognitional presence of the real" departs from the "immediate physical presence of the real." Our ability to do this indicates that we have sufficient grasp of the reality behind the relativity that is intrinsic in perception to be able to correct for the latter. Thus we can explain why the color blind man does not see color, whereas the normal man does, and we can even invent tests to determine whether someone is color blind and whether he suffers from monochromacy, dichromacy, or trichromacy. We can explain, by understanding refraction and the effect that a change in medium has on the direction of light waves as a result of a modification of their speed, why the image of the twig in the water appears bent. We can explain why vantage point affects our perception of the shape seen. We can explain why the velocity of an object that emits sound affects the pitch of the sound. These adjustments, it would seem, would be impossible if we did not have a grasp of the underlying reality behind the relativity in perception. Moreover, the "relativity in perception" is itself part of reality, as it would not be reflective of reality if my senses did not take into consideration changes in media, in velocity, in vantage point, and so forth.
In summary, the objections of the empiricists seem rather easily overcome. They surely are not sufficient to have us jettison our common sense and advocate a total lack of correlation between the real about us, and our cognition of that real world within us, a cognition that is mediated through the sufficiently reliable senses.
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