L. Susan Stebbing
L. Susan Stebbing was an analytic philosopher (she was a founder of the journal Analysis in 1933) and logical positivist. Her 1939 book Philosophy and the Physicists was a critical analysis of the idea that quantum indeterminacy was a proper basis for human freedom. "The Physicists" referred to in the title were primarily Sir Arthur Stanley Eddington and
Sir James Jeans, two of the greatest science popularizers of the day. Stebbing felt that
they had an undeserved influence on popular opinion.
"They are not always reliable guides. Their influence has been considerable upon the reading public, upon theologians, and upon preachers; they have even misled philosophers who should have known better. Accordingly, it has seemed to me to be worth while to examine in some detail the philosophical views that they have put forth and to criticize the grounds upon which these views are based.With delicious irony, Stebbing notes that for many years physicists had claimed that deterministic laws could explain everything about the universe and its contents, even the human mind. Suddenly, the same men were saying that, on the contrary, the world could only be known probabilistically.
"Undoubtedly the bearing of the Law of Universal Causation ' (to use a favourite nineteenth-century phrase) is a problem much in evidence in the discussions of our philosophizing scientists. It is commonly admitted that at one time the scientists were informing us that 'free will' was an illusion, that we were all constrained to act — in whatever way we did in fact act; that if we were wicked, it couldn't be helped, and if we were good — well, that was nothing to be complaisant about. Nowadays, it is commonly supposed that these conclusions were premature, that if the biologists were compelled to deny to us freedom of action that was because they did not see sufficiently deeply into the constitution of matter; now, however, the physicists have come to our rescue and have argued that, if an electron is 'free to choose' where it will go, surely a man may choose whether he will spend his summer holidays at Margate or at Wiesbaden, or whether he will propose to an heiress or remain a bachelor. Along with this proclamation of the rights of the intuition of free will, based somehow upon its being something other than an intuition — namely, a deliverance of consciousness in conformity with the most refined knowledge of the expert physicist — there goes an increasing reliance of the common reader upon the ability of the physicist to tell us what will happen to some one looking at the sun from the Cornish Coast on 11 August 1999, and what will happen to the non-combatants in the next world war. "The situation is sufficiently curious. Upon the one hand we rely increasingly upon the scientist, biochemist, physiologist, and physicist, to tell us how to breed men and women for a 'brave new world' and what, if we disregard their advice, will happen to our descendants; on the other hand, we rejoice to be told that the physicist is less certain now than he was a few years ago that he does, or ever can, know what will happen. The position assigned to science in general, and to this or that particular scientist, is curious enough. We common readers continue to look up to them as the repository of knowledge and begin to regard them as the custodians of the spiritual element in the universe. They — or to speak more moderately some of them — have long aspired to the mantle of the prophets; now we thrust the mantle upon them. Theologians have, in the past, claimed to speak with a higher authority about higher things than those with which the scientist is concerned; now the theologians hang on to the mantles — or is it only the coats? — of the popularizing scientist. The situation does not lack an element of comedy.Of course many scientists could not accept real indeterminacy. They included some of the greatest thinkers, including Max Planck, who proposed 1n 1900 the famous "quantum of action" h, Albert Einstein, who in 1905 showed that Planck's h implied that energies were indeed discrete or "quantized," and Erwin Schrödinger, whose 1926 equation of motion for the "wave-function" of atomic-scale objects remains deterministic until there is a "collapse of the wave function." It is this collapse or "reduction of the wave-packet" that introduces indeterminacy, and only on the microscopic atomic scale - unless it is "amplified" into the macroscopic world, for example by a Geiger counter. Stebbing compares Planck, as an example of those scientists who say causal (deterministic) explanations are the very essence of science, with Eddington, who (along with Neils Bohr, Max Born, and Werner Heisenberg) accepted indeterministic "uncaused causes."
"The main point at issue between Planck and Eddington is, then, not whether the scientist believes that his procedure is rational or whether this belief springs merely from an ungrounded faith; it is whether a rational procedure must be based upon the assumption of deterministic laws. Planck says that it must be so based. Eddington says that it is not now so based. Although he is fond of calling attention to the modesty of this claim, he is not content with making it. Unfortunately he rashly adds that science does not offer a particle of evidence in favour of determinism. This statement surely requires some examination. For the purpose of such an examination it seems to me to be necessary to consider three closely connected questions. These questions are: (1) Is there any sense in which it is true to say that science has been based upon determinism?; (2) what is the connexion between determinism, prediction, and rationality?; (3) why should there be so much glee or so much gloom at the rejection of determinism? Perhaps it does not seem obvious that these questions are closely connected, but I think it will be found by no means easy to disentangle them in the discussions of the scientists with whom we are mainly concerned. (1) We have already seen that scientists have certainly believed that science was based upon determinism. Moreover, were that not the case there would have been no occasion for rejoicing or mourning, nor could we have spoken of 'the decline of determinism'. Indeed, Eddington insists that the withdrawal of physical science from an attitude it had adopted consistently for more than 200 years is not to be treated lightly' (N.P.Sc. 73). But to say that 'science is based upon determinism' is to say that scientists have based their work upon determinism. There is no science apart from the minds of men. Accordingly, we can say loosely that science is based upon determinism, provided that the procedure of scientists has been deterministic and that no alternative to this procedure can be consistently carried through. But, if it be true that 'so far as we have yet gone in our probing of the material universe, we find no evidence in favour of determinism', it must be concluded that the work of earlier scientists has been based upon an illusion. This is, indeed, what Eddington wishes to maintain. I think that there is a sense in which it is true, but to describe the acceptance of determinism as the acceptance of an illusion is, I believe, more misleading than helpful.Stebbing takes issue with Eddington's basic idea that the indeterminacy of electrons, making them "free to choose," in any way helps with human freedom. "Although the door of human freedom is opened," she quotes Eddington as saying, "it is not flung wide open; only a chink of daylight appears." She asks, "How is the door to be prised open wide enough to let in the full daylight?" (p. 215)
"I cannot help thinking that Eddington is on the wrong tack in trying to rest any part of the case for the freedom of man upon the present acceptance of indeterminism in physics....his argument may perhaps be stated as follows: If previous physical events completely determine all the movements of my body, then the movements of my pen are also completely determined by previous physical events. But the movements of my pen express the results of those mental processes that we call reasoning and seeking for truth. But if the movements of my pen are completely determined by previous physical events, how can it be held that my mental processes have anything to do with the movements made by my pen. And if my mental processes have nothing to do with the movements of my pen, how can we explain the importance attached to those movements of my pen which record what is true? This argument seems to Eddington to explain reasoning away, and to make of it a process quite other than he feels it to be. I agree that there is a difficulty; it is the difficulty of the gap between conscious processes and physical events.