Berkeley’s Psychological Criticism of Newton
The genius of Newton lay in the field of mathematics and physics. When he let his thought wander beyond this province, the results were of doubtful quality. The Principia was the great cornerstone for the edifice of science that was to be erected in the following centuries, but the definitions and theoretical excursions in the scholia could only arouse the vehement criticism of philosophers. In particular Newton exposed himself to criticism with his proud declaration of autonomy for the new science. Physics could go its course, as it actually did, conscientiously applying the well-established methods to observed phenomena, without regard for the debates of metaphysicians. The Scholium Generale had announced the precept hypotheses non fingo: “whatever is not deduced from the phenomena is to be called an hypothesis; and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy.” The assumption of absolute space was a glaring contradiction to this declaration; certainly this fundamental “hypothesis” was not deduced from the phenomena.
We shall not be surprised, therefore, when now we turn to Berkeley and his criticism of Newton’s theory, to find some pungent remarks concerning the boundaries between physics and metaphysics. In his De Motu (1721) Berkeley writes:
For the rest, it would be convenient, setting aside that it is a well established custom, to distinguish between sciences in such a manner that each is well circumscribed by its proper boundaries. The philosopher of nature should remain entirely with his experiments, his laws of motion, his mechanical principles and the conclusions derived therefrom; if he has something to say on other matters, he should relate what is accepted in the respective higher science.
The context leaves hardly a doubt that the remarks about the philosophus naturalis are meant to put Newton in his place.54 Berkeley’s criticism of Newton’s theory moves on two planes. With regard to the method of physics he returns to the principle of relativity. A body can be recognized as moving only in relation to another body that is relatively at rest. The idea of absolute motion is incompatible with the conditions of experience. Motion can be measured only by things given to the senses. Since absolute space is not given to the senses, it cannot be used for the distinction of different types of motion. The conception of an absolute motion is impossible.55
Relativity and Human Psychology
Moreover, in empirical science we do not need such a conception. All that we need is a system of reference that permits us to distinguish between bodies that are relatively at rest or in motion. And such a system we have given in the heaven of the fixed stars. We do not need the assumption of an absolute space for the formulation of the laws of motion because they are valid if we use the fixed stars as the system at rest instead of absolute space.56 The laws of motion are generalizations from observations and no more. We must “distinguish between mathematical hypotheses and the nature of things.” Motion belongs to the world of senses, and we must be satisfied with relative measurements.57 Berkeley’s second approach to the problem lies on the way of a psychological analysis of the illusions that lead to the assumption of absolute space. The idea of a space without a content is empty, it is a merum nihil.58 We are deceived, however, into the assumption because in speculating on the problem of space we subtract all bodies but forget to subtract our own. If we imagine space emptied of all content we still have an experience of space because we have the experience of our body and of the movements of its members. The experience in itself is not deceptive, but what we experience is the relative space defined by the parts of our body. The attribution of absoluteness to this space is a fallacy.59 The meaning of the somewhat brief passages in De Motu becomes clearer through the more discursive analysis in the Principles of Human Knowledge. As far as the observation of moving bodies is concerned, says Berkeley in the Principles, we never can observe anything but bodies moving relatively to each other. The physicist is such an observer of moving bodies, and hence in physics nothing can be admitted but a concept of relative motion. Nevertheless, we not only observe motion, we can also experience it.
Now, I ask any one whether, in his sense of motion as he walks along the streets, the stones he passes over may be said to move, because they change distance with his feet? To me it appears that though motion includes a relation of one thing to another, yet it is not necessary that each term of the relation be denominated from it.60
Berkeley, thus, recognizes the experience of absolute motion, but he considers it impermissible to inject this experience into mathematical physics. The laws of science can only describe the observed motions, and observed motions are relative.
Absolute Motion: True for People and for Physics?
Knowingly or unknowingly, Berkeley has touched with this argument on one of the actual historical roots of the Newtonian conception of absolute space. In his correspondence with Descartes, Henry More had advanced the experience of absolute rest and motion as an argument against Descartes’s radical concept of “reciprocal” movement: “When I am sitting quietly, and another man who moves away, let us say a thousand steps, becomes red in his face and fatigued, while I who am sitting do not become red-faced and fatigued, it certainly is he who has moved, while I have been at rest during the time.”61 More used the experience of absolute motion as an argument against relativity. This double use to which the argument could be put (for or against relativity) indicates the insufficient differentiation of problems that characterizes the state of theory at this period. It indicates also, however, that the problem of absolute motion has its complexities. Berkeley was of course right when he protested against the injection of experienced absolute motion into the description of observed relative motion. Nevertheless, we are faced with the fact that there are some bodies in the universe, namely human bodies, who know when they are in absolute motion and when at absolute rest. One may eject absolute motion from physics, but the problem will reappear on the level of speculation, and with it there will reappear the problem of absolute space. The difficulties that Galileo had with the Inquisition appear now on the level of a conflict between the relative motion of physics and the analysis of the experience of absolute motion. The relativity of motion in science does not abolish the problem of an absolute order of the universe that is revealed and centered in the experience of man. The complexity of the problem showed itself in the opposite use that Berkeley and More could make of the argument from absolute motion. It shows itself, furthermore, in the opposition of purpose between the two thinkers. More wanted absolute space to serve as the immaterial, divine fundamentum of infinite phenomenal space in order to save the existence of God. Berkeley wants to get rid of absolute space for precisely the same purpose. The chief advantage that arises from the elimination of absolute space “is that we are freed from the dangerous dilemma … of thinking either that Real Space is God, or else that there is something beside God which is eternal, uncreated, infinite, indivisible, immutable. Both which may justly be thought pernicious and absurd notions.”62 Berkeley has achieved his purpose of saving God by disentangling him from the space of physics–but this saving action does not solve the problem of space. His psychological analysis has led us a good step deeper into the problem. It has brought the distinction between generalizations from observed phenomena in physics and the realm of human experience, but it has left the problem of absolute space more or less where it was before.
The Deadlock: Fitting the Philosophy to the Physics
A psychological analysis of the Berkeleyan type can dispose of the concept of absolute space as a merum nihil, it can trace the idea to its origin in the experience of the body, it can show the fallacy of hypostatizing this experience into an objective quality of phenomenal space, and–what is most important for Berkeley–it can by such effective criticism clear the way for the philosophia prima. It cannot, however, persuade a physicist to consider his problem solved. When Galileo discovered the law of motion he did not consider a body at rest in relation to the fixed stars. He considered it absolutely at rest. The laws of science are meant to be valid absolutely. As a follower of Newton expressed it:
From the observation of nature we all know that there is motion, that a body in motion perseveres in that state, till by the action or influence of some power it be necessitated to change it, that it is not in relative or apparent motion in which it perseveres in consequence of its inertia, but in real and absolute space.63
If we assume with Descartes that the place of a body is determined by its relation to the bodies in its neighborhood, the law of motion would have to announce that a body on which no external force is applied cannot change its position with regard to the surrounding bodies. This law is absurd because obviously the relative position can be changed by applying forces to the surrounding bodies. In brief: the criticism of the philosophers, as Berkeley did with Newton, is not constructive. As far as physics is concerned, the only result will be that the physicists will have to put them in their place. And this is what actually happened through Leonhard Euler in his Réflexions sur l’espace et le temps (1748). The philosophers were told that the certainty of the laws of mechanics must be the starting point of the inquiry. Any criticism that is in conflict with those principles must be rejected, however conclusive in itself it may be. The metaphysical principles must be chosen in such a manner that they will be compatible with physics. The physicists and their philosophical critics had come to a deadlock. It was a deadlock with rather grave consequences. If we take Euler’s demand seriously and generalize it, we arrive at the rule that every time an empirical scientist makes a mess of his fundamental concepts–which is a rather ordinary occurrence–the philosophers would be faced by the alternative of either clearing up the mess for him, or of henceforth talking nonsense in epistemology and metaphysics. The demand has a touch of the burlesque. Nevertheless, it could be imposed with a measure of success. The graveness of the situation may be gathered from the fact that even Kant submitted to it, after some vacillation, at least to the extent of recognizing the Faktum der Wissenschaft including Newton’s absolute space.64 Before we elaborate, however, on this curiosity of our intellectual civilization, we must briefly outline the further differentiation of the problem of absolute space and the solution toward which it tended.
Revolution and the New Science History of Political Ideas, Volume VI (CW Vol 24 ) Chapter 3 “The English Quest for the Concrete” §3. Absolute Space and Relativity pp 194-199 A number of similar excerpts can be found HERE.