…the molecular basis of biology shows that biological processes are governed by the laws of physics and chemistry and therefore are as determined as the orbits of the planets. Recent experiments in neuroscience support the view that it is our physical brain, following the known laws of science, that determines our actions and not some agency that exists outside those laws…so it seems that we are no more than biological machines and that free will is just an illusion (Hawking and Mlodinow, 2010, emphasis added).
It is important to point out that physicists are not the only scientists who espouse an uncompromisingly deterministic perspective. For example, Sam Harris, a neuroscientist, states:
Free will is an illusion. Our wills are simply not of our own making. Thoughts and intentions emerge from background causes of which we are unaware and over which we exert no conscious control. We do not have the freedom we think we have (Harris, 2012, p. 5, emphasis in original).
An intelligence knowing all the forces acting in nature at a given instant, as well as the momentary positions of all things in the universe, would be able to comprehend in one single formula the motions of the largest bodies as well as of the lightest atoms in the world, provided that its intellect were sufficiently powerful to subject all data to analysis; to it nothing would be uncertain, the future as well as the past would be present to its eyes (Quoted in Weinert, 2004, p. 197).
Now, if the law of forces were known, and the position, velocity and direction of all the points at any given instant, it would be possible for a mind of this type to foresee all the necessary subsequent motions and states, and to predict all the phenomena that necessarily followed from them (Quoted in Barrow, 2007, p. 63).
Thus, the most extreme versions of determinism assert that–even though it would require some form of superhuman omniscience (aka, God) to obtain knowledge of every, law, particle and interaction in the cosmos–nothing moves, interacts, appears or disappears in the clockwork universe without having been minutely pre-determined by a chain of causality that was set in motion at the origin of the universe. This version of hard-core determinism leaves no room whatsoever for either agency or indeterminism.
In classical physics it would have been legitimate to specify exactly both the position and the momentum of a given particle at the same time, but in quantum mechanics that is forbidden, as is well known, by the uncertainty, or indeterminacy, principle. The position of a particle can be specified exactly, but its momentum will then be completely undetermined (Gell-Mann, 1994, p. 139, emphasis added).
Another most interesting change in the ideas and philosophy of science brought about by quantum physics is this: it is not possible to predict exactly what will happen in any circumstance…nature, as we understand it today, behaves in such a way that it is fundamentally impossible to make a precise prediction of exactly what will happen in a given experiment (Feynman, 1965, p. 35 – emphasis in original)
Interestingly, well acquainted as Hawking certainly is with quantum uncertainty, he still insists that determinism holds up even in the face of fundamental physical uncertainties:
…there is still determinism in quantum theory, but it is on a reduced scale…in quantum theory the ability to make exact predictions is just half what it was in the classical Laplace worldview. Nevertheless, within this restricted sense it is still possible to claim that there is determinism (Hawking, 2001, p. 108).
This is a curious assertion. Is it logically coherent to argue that, in a universe where we can predict, at best, 50% of potential outcomes, hard determinism persists?# Is Hawking’s conviction an expression of dogmatic faith, or a dispassionate analysis of objective facts? Wouldn’t it be more appropriate for Hawking to concede that there is as much indeterminism in the universe as there is determinism?
Interestingly, Hawking and Mlodinow (2010) answer this very question in the negative:
According to quantum physics, no matter how much information we obtain or how powerful our computing abilities, the outcomes of physical processes cannot be predicted with certainty because they are not determined with certainty. Instead, given the initial state of a system, nature determines its future state through a process that is fundamentally uncertain. In other words, nature does not dictate the outcome of any process or experiment, even in the simplest of situations (Hawking and Mlodinow, 2010, p. 72, emphasis in original)
Crucially, Hawking and Mlodinow concede that, in spite of the Laplacian hard determinist claim that it is theoretically possible to know everything about everything, because of the bizarre and uncertain behavior of quantum particles, Hawking and Mlodinow own up to the all-important revelation that it will never be possible to know everything about anything: “nature does not dictate the outcome of any process or experiment, even in the simplest of situations.” This is a crucial point to re-emphasize: The universe cannot be deterministic if it is impossible to determine the precise characteristics of even a single quantum particle. Therefore, Hawking and Mlodinow proclaim the death of Laplacian hard determinism.
However, Hawking and Mlodinow’s self-contradictions do not end there. Only a few sentences later, Hawking and Mlodinow reverse themselves yet again:
Quantum physics might seem to undermine the idea that nature is governed by laws, but that is not the case. Instead it leads us to accept a new form of determinism: Given the state of a system at some time, the laws of nature determine the probabilities of various futures and pasts rather than determining the future and past with certainty (Hawking and Mlodinow, 2010, p. 72, emphasis in original).
In spite of what Hawking and Mlodinow suggest, Laplacian hard determinism is an essentially either-or proposition. Either the universe is 100% deterministic, or it isn’t. However, according to Hawking and Mlodinow, determinism is “definitely probably” at work in the universe. And you can quote them on that!
Hawking and Mlodinow’s equivocations read more like a case of paradigm crisis-inspired denial than a valid update on the concept of determinism. Further, I don’t think Laplace would accept Hawking and Mlodinow’s ambivalent re-characterization of indeterminism as determinism.
Barrow, John D. New Theories of Everything: The Quest for Ultimate Explanation. Oxford: Oxford University Press, 2007.
Feynman, R. P., R. B. Leighton, and M. Sands. The Feynman Lectures on Physics: Quantum Mechanics: Volume III. Reading: n.p., 1965.
Hawking, Stephen W., 2001. The Universe in a Nutshell. New York: Bantam Books.