5. The Objectivity of Sense Knowledge
It is on this aspect of sense perception that we find the most complete opposition between the ancient and Scholastic doctrine, which is on the side of realism, and the newer philosophies, which run to subjectivism. The question is whether the senses give us a grasp of the external world as it really is; or whether our sense knowledge is only an approximation to reality, that is, only more or less objective; or, going yet further, whether it is a mere symbolical awareness, that is, only a symbol of reality, and nowise an immediate apprehension of external things.
The matter under discussion here is the objectivity of the proper and common sensibles only, and of the latter simply as perceived by an external sense, and not necessarily as interpreted by the internal senses. Therefore, we are not now speaking of the objectivity of the sensible per accidens, nor, as we have said, of that aspect of perception in which the internal senses or the intellect elaborate on the immediate data of sense. The present discussion, moreover, represents only one phase of the wider problem regarding the objectivity of knowledge in general. We shall consider the problem from its broader point of view when treating of the intellect and the apprehension of being. Ilere, then, the point of inquiry pertains only to the immediate datum of each external sense.
a) The position of Aristotle and St. Thomas. - On this question the position of Aristotle and St. Thomas is one of unequivocal realism or objectivity; in their view the immediate data of sense are objective. But they are not unaware of the complexity of the problem, showing themselves wise and circumspect in stating their position. From the outset, Aristotle in particular is careful to leave the way open for qualifications, but without prejudice to his fundamental thesis. What he wants above all to refute is the theory of Protagoras, who seemed to think that when sensation ceases, the object likewise ceases to exist. That the object which produces the sensation should vanish just because the sensation is interrupted, such a view, declares Aristotle, is impossible and absurd. Sensation is certainly not of itself. Apart from sensation there is something else that necessarily exists prior to it.18 Aristotle, moreover, repeats again and again that in the act of sensation there exists an identity or oneness between the sensible object and the sentient subject, between the perceived and the perceiver. Hence, with respect to the proper sensibles there can be no error in the senses. St. Thomas also affirms the objectivity of sensation, doing so in terms that exclude all ambiguity. As an example, take the following remark on color. "Sight," he says, "sees the color of the apple apart from its smell. If therefore it be asked where is the color which is seen apart from the smell, it is quite clear that the color which is seen is only in the apple." 14 Once again, however, we must be warned as to what the realism of St. Thomas and Aristotle does and does not entail. We have already said that it pertains only to the proper sensibles and to the common sensibles as perceived by an external sense; also, that it refers only to the external accidents, for the essence of n thing is not within the reach of the senses. In addition, it is well to remember that sense itself cannot formally judge the objectivity of its knowledge, since this activity presupposes reflection in the strict sense of the word and is therefore found in intellect alone.
There are other qualifications to be noted. In more than one place St. Thomas, speaking of error in the senses, explicitly acknowledges a certain relativity in sense knowledge 15 It is a fact of common experience, lie remarks, that a thing seems small or large according to the distance from which it is seen. It is the nearer view one must take as the basis for an objectively true judgment. Similarly, the color of a thing may change with distance. Here again the nearer view is the correct one. Besides, the common sensibles may be the occasion for many false impressions. Even the condition of the sense organs has to be reckoned with; if these arc diseased or otherwise abnormally affected, as in fever and jaundice, sensation itself is correspondingly marred and disturbed. To add to this, the general bodily disposition of the perceiving subject can be a source of error. To one who is physically weak, a light object may give the sensation of being heavy.
Considering, therefore, the various provisos we find in St. Thomas, we may assume that if he had had the benefit of the many additional facts brought to light by the methods and techniques of modern psychology, he would have been disposed to make even further concessions in the direction of relativism. Nevertheless, the basic position remains that for him as for Aristotle the sense faculty is, in the first instance, devoid of all content; that all of its specification comes from the object; and that under normal conditions at least, we perceive the sense qualities as they are in reality.
b) The contributions of John of St. Thomas. - In general, the commentators of St. Thomas follow the aforesaid doctrine regarding the objectivity of sense knowledge, elaborating it here and there with refinements of their own. Of such additional developments John of St. Thomas offers as many, perhaps, as anyone else, if not more.16 There are two points in particular that he underlines with respect to the doctrine of realism in sense knowledge.
His first observation is that sense knowledge is experimental or intuitive, as compared with the abstract knowledge that the intellect has when it grasps, in a direct but abstracted concept, the essence of the concrete reality. Experimental knowledge means, and this is essential to it, that the known object is physically, that is, concretely, present to the faculty of knowledge. John of St. Thomas insists that unless we hold to this immediate quality of sense knowledge, not only its own objectivity but also that of intellectual knowledge is in jeopardy, because thought begins with, and ultimately rests on, the knowledge of the external senses.
In a similar concern to safeguard the immediacy of sense knowledge, John of St. Thomas declares that the sense, in contrast to the intellect, does not attain its object through the formation of an expressed species. Sense knowledge - leaving aside the internal senses - has no other term than the thing itself or its objective qualities, which are known immediately by the senses. Such an expressed species is not needed here because the thing itself, in its concrete reality, is present with such a directness that it can be apprehended immediately and thus be the term of the act of knowledge. Another reason is that an act of knowledge, being an immanent activity, belongs to the predicament of quality, and so does not necessarily require the production of a term. In the present instance, namely in external sense knowledge, the thing itself contains whatever is needed to terminate the act of knowing. The production of an expressed species as the term of this knowledge would not only be superfluous, but also ruinous to its immediacy, and therefore to its objectivity.
e) Some modern Thomists on the relativity of sense knowledge. - The extensive investigations of modern psychology have brought to light a variety of problems regarding sensation. In their anxiety over these problems some modern Thomists have undertaken to revise the older doctrine by giving it a more relativist leaning."
One of their important changes from the standpoint of objectivity consists in giving the primary qualities (quantitative aspects) a preferred status over the secondary qualities (qualitative aspects). According to this understanding, the attribute of extension in its various forms is grounded in reality as we perceive it, but the qualitative aspects of our sensory impressions are not objective. Even if there is something in reality that corresponds to each quality perceived, and thus forms the basis for the specification of sensation, there is no authentic likeness between the quality as perceived and as existing in reality. Such a view, of course, is nothing less than a radical transformation of the older doctrine. For St. Thomas it is precisely in the perception of the proper sensibles (qualitative aspects) that we have the greatest guarantee of objectivity; error, if it occurs at all, arises only in connection with the perception of the common sensibles (quantitative aspects).
Not all Thoinists carry their revisions to such extremes. According to some the perceived sensible is objective, and known immediately, but it is not fully realized or actualized before contact with the sense organ and the sense faculty. Since, moreover, it is thought that both the external environment and the disposit ion of the organ or the subject may greatly modify the circumstances attendant upon sensation, the upshot of this interpretation is that the object as existing in reality is not necessarily identical with the psychological representation we have of it.
d) Conclusions. - Wlhat is one to make of these newer explanations? There is no doubt that St. Thomas, following Aristotle, unequivocally affirms the objectivity of sense qualities. It is also certain that when the facts demanded it, he did not hesitate to allow for a certain amount of relativism alongside of his basic position. The question is whether we can go beyond these concessions made by St. Thomas. The answer would seem to be a clear-cut yes. There is no reason why we should not, for example, make even greater allowance than he for the role of the medium and the sense organ; why, in other words, we should not admit that the object as perceived by us is not the object in its naked reality, as it were, but as somehow existing on the level of the sense faculty, which has a certain influence on how the object is perceived.
But may we go even further and say that sense qualities as perceived are mere symbols of the real qualities of things, very useful symbols, it may be, but nothing more. The very nature of sense makes it impossible to give an absolute answer to this question on purely empirical or introspective grounds, because sense, unlike intellect, lacks the power to reflect on its act and to determine the precise validity of its knowledge. Be that as it may, one thing remains certain. If we want to cling to the Thomist doctrine of sensation, we must also adhere to the basic immediacy and objectivity of sense knowledge.