The evolution of scientific thought from Newton to Einstein

by A. D'Abro

It is scarcely necessary to mention that those philosophers who deny the legitimacy of the views just expressed, claiming our knowledge of external reality to be a matter of direct apprehension, find themselves in a very embarrassing position when such commonplace phenomena as mirror-images are considered. It is all very well for them to say that the results of visual perception may have to be corrected subsequently by varying the conditions of observation and taking into consideration all other perceptions. But the fact is that if this visual perception is to be regarded as revealing reality directly, i.e., as fundamental, its disclosures should be beyond dispute and it would be meaningless to correct them. For we can correct a datum only in virtue of other criteria, which are then automatically regarded as more fundamental. In the present case the philosopher’s argument would indicate that the result of a co-ordination of perceptions in general, is to be taken as more fundamental than bare visual perception or bare auditory perception, etc. But inasmuch as the disclosures of no one of the individual perceptions that enter into the co-ordination can be accepted without a possible danger of correction, we must go back farther, behind the individual perceptions, to the sensations whose recognition is untainted by any trace of inference. We then arrive at our original conclusion, namely, that knowledge springs from a co-ordination not of perceptions, but of sensations.

Let us consider another example. The neo-realist would probably state that when we say, “I hear a bell,” no element of inference need enter into this knowledge. But a contention of this sort would of course be untenable, for the only reason the auditory sensation yields us any knowledge of the bell is because, in view of an association of ideas issuing from past experience, we have come to connect a certain class of auditory sensations with the presence of a bell. A man who had seen bells, but had never heard them clang would not attribute the sound to the bell any more than a man who had never encountered rattlesnakes or been told of their existence would ever say: “I hear a rattlesnake.” On the other hand, a man who had previously come into contact with these reptiles would be just as apt to say, “I hear a rattlesnake,” as the philosopher to say: “I hear a bell.” Obviously, past experience, and not direct recognition, is at the root of this knowledge. In the absence of past experience, all we could say would be, “I sense a sound,” and then try to describe the sound by reproducing it, as nearly as possible, with our tongue and lips.

With visual perceptions our conclusions will be exactly the same, but at first sight it might appear that the problem was slightly different, for even had we never seen a snake before, we should still be able to say, “I see a creature with a long, thin body,” and then proceed to coin some name for it. But it should be remembered that although we might never have seen a snake before, yet a snake is a particular instance of an object, and unless we had always been blind we should have seen objects ever since infancy. If, then, we wish to obtain a parallel to the case of the rattlesnake (as we applied it to auditory perceptions), we must start with a blind man who has felt objects but never seen any. Then, assuming he were suddenly endowed with eyesight, the question is whether he would identify immediately, by a mere act of intuition, the colours and shapes he would now see, with the table he had previously explored with his hands. This is precisely what we have every reason to doubt. We may now proceed to a more detailed discussion of the knowledge-problem.

Here it should be clearly understood that we are merely seeking to establish a hierarchy of knowledge following the psychological order according to which human knowledge appears to have arisen. We may therefore consider the faculty of unreasoned sense-awareness as furnishing the initial data which it is necessary to accept before we are in a position to speculate any further. Together with our awareness of sensations we have to consider our awareness of thoughts or ideas. Whether, in the absence of sensations, thoughts would still have originated, is a question which does not concern us. At all events, an answer to it seems impossible, for we cannot study the thoughts of a living corpse.

Next we have to consider our awareness of the passage of time. This awareness appears to be closely allied with the faculty of memory. Indeed, it is only thanks to the memory of sensations or ideas that we can differentiate the present from the past. It is probable, therefore, that to a being devoid of all trace of memory, to a being sensing but the present, past and future would convey no meaning and the passage of time would be unthinkable. Again, whether, in the absence of our awareness of sensations or ideas, memory would have anything left to remember, is a question which need not detain us. The reason for this omission is, of course, that in the present survey we are considering normal human beings; and with these an awareness of sensations, ideas, and of the flowing of time is known to exist.

Our recognition of the simultaneity of two sensations is fundamental, in that it cannot be analysed further. The same fundamental nature must be credited to our recognition of a succession of sensations or ideas. For this reason a sense of simultaneity and succession (when referring to our awareness of sensations or ideas, and not, of course, to a simultaneity of spatially separated events) must serve as a basis for subsequent knowledge.

We have also to mention our judgments of constancy, invariancy or sameness. Thus, we recognise two sensations or two groups of sensations as identical, or, again, we judge them as subsisting unmodified through time. Although all these seemingly a priori basic sources of information are of a widely different nature, we may consider them as a whole in our future discussions.

Now, had men confined themselves to registering sense impressions and to sensing the flow of time, there could never have arisen such a thing as scientific knowledge or even crude commonplace knowledge. Somehow or other the initial facts had to be co-ordinated and interconnected. Only thus could a coherent form of knowledge leading to prevision become possible. It is to this synthesis of our sense impressions, supplemented by the fundamental forms of recognition we have mentioned, that we owe our belief in an external universe of space, matter, force and colour. In this universe, time was assumed to be flowing, events were regarded as exhibiting causal relationships; and our sense impressions were attributed to common causes existing in a public objective universe.

It is probable that a belief in causal connections arose from our ability to produce and to arrest certain sense impressions at pleasure through the conscious action of our will. Thus, we “will” a certain effort (which turns out to correspond to the closing of our eyes), and the luminous impression ceases. It was then but a short step to extend our belief in causal connections to sequences of events in the outside world, even though in this case the human will was known to play no part. The same with force. Though suggested originally by our awareness of effort, it was soon exteriorised and credited with an existence in the outside world; and a similar process of exteriorisation would appear to have been responsible for our belief in physical time (no longer the “I” stream of our consciousness), in a time regarded as enduring in the outside universe regardless of our presence.

It does not seem to be of great interest to question whether these exteriorisations of the dehumanised concepts of causal connection, force and time were justified or not. In any case it cannot be denied that the exteriorisation of causal connections, for instance, has proved of inestimable service in allowing us to account for the routine of our experience. Therein resides its justification, since causality appears to be an indispensable condition for the sequence of phenomena to be intelligible, hence for prevision to be possible. But it would seem scarcely correct to state that the understanding imposes causality on an indifferent world; for, as we know, there are regions of science where, although causal connections may be suspected, none have yet been established.