Conflict between determinism and indeterminism

Determinism in science had its origin in the philosophical musing of the French polymath René Descartes. According to his 1644 Principles of Philosophy, the physical world is a “deterministic machine”, where events are the inevitable and necessary consequences of antecedent events. 

Descartes’ concept of scientific determinism was rationalised by the laws of motion and gravity postulated by Isaac Newton in 1687.  Much to the delight of the determinists, the laws allow us, in principle, to calculate and predict with clockwork precision every outcome in nature, under all conditions, as long as we know enough about what are called initial conditions. Hence, Newtonian physics, also known as classical physics, was and still is considered by many thinkers to be the paragon of determinism. They even apotheosized classical physics to be the omniscience of God who encompasses all knowledge of the universe - past, present and future.
Subsequent to Newton, the French mathematician and physicist Pierre-Simon Laplace, a believer in causal determinism, speculated in the introduction to his 1814 ‘Essai Philosophique sur les Probabilités’ that if someone, since dubbed as Laplace’s Demon, determined the entire history of the universe, down to the last detail, then both the future and the past would hold no secrets whatsoever. This implies that the Universe, since its creation 13.7 billion years ago, is a gigantic clock, unwinding relentlessly along a rigid, pre-determined pathway towards an unalterable final state.
In the first decade of the 20th Century, nature had a surprise in store for the determinists. They saw their world subverted when several studies of subatomic particles exposed many phenomena that couldn’t be satisfactorily explained within the framework of deterministic classical physics.
Determinism became irrelevant after physicists developed quantum mechanics to study the subatomic world. It casts reasonable doubt on the traditional determinism of classical physics by offering us a unique way of studying the structure of the physical universe in a way that was undreamt of in Newton’s days.
Unlike classical physics, quantum mechanics makes a clear-cut distinction between what can be known in principle and what is actually known by observation. This is manifested in Werner Heisenberg’s famous uncertainty principle, which states that we cannot measure the position and momentum of subatomic particles simultaneously with arbitrarily high precision. As the cornerstone of quantum mechanics, the principle assures us that there’s always an irreducible indeterminism in the operation of subatomic systems, thereby, rendering the concept of determinism in science irrelevant.
Moreover, the basic principles of quantum mechanics tell us that nature is inherently unpredictable. As an example, we don’t know how an electron in an excited state knows to which lower energy state it should jump, or when to jump. In fact, the electron doesn’t know anything about itself a priori. Neither does quantum mechanics, it can only predict the probability of when and to which state the electron will jump. In other words, we cannot know exactly how something will turn out before it actually happens.
The view that nature is governed by probability rather than certainty flustered Albert Einstein, a staunch believer in a deterministic universe. Despite being well aware that quantum mechanics had survived stringent experimental tests, he famously said, “God doesnot play dice with the universe.” Einstein maintained that if quantum mechanics “were correct then the world would be crazy.” According to him, “God created Newton’s laws of motion and the necessary masses and forces. That is all; everything else follows by deduction upon development of suitable mathematical methods.”
As for others who believe that events in the universe are fully predictable, without ambiguity or uncertainty, they recoiled at the idea that classical physics could no longer claim to predict the outcome of events with infinite precision. Nevertheless, in defense of classical physics, they argue that our inability to predict any more than probabilities is simply due to ignorance. Proponents of quantum indeterminacy, on the other hand, contend that the probabilistic nature of quantum mechanics is an inevitable consequence of the failure of causality in reality.
Why were Einstein and other determinists troubled by a theory that works flawlessly? They were troubled not because quantum theory violates intuition and common sense. They were troubled because objects in quantum mechanics are neither particles nor waves, but a combination of both. They were troubled because quantum mechanics deals with ghostly, unobservable quantities, makes probability fundamental, and leaves the boundary between quantum realm and the realm of human perception quite vague.
Most determinist eventually accepted the underlying uncertainty in quantum mechanics, albeit reluctantly. They, however, believe that there’s probably a fundamental flaw in quantum mechanics that gives rise to indeterminism. Perhaps, there’s some “hidden variable” that one day could allow them to predict things with perfect certainty again.They are still waiting for that one day.
The remoteness of quantum phenomena from everyday experience may belie common sense. But we have to realise that physics of the past hundred years has taught us that common sense is a poor guide in the new realms of knowledge. It also taught us that science progresses by breaking the rules of the past. As we move from one level of reality to another in the study of nature, the laws and concepts used to describe it must change accordingly. n

The writer is a Professor of Physics at Fordham University, New York.

Photos: Google Images. 

Conflict between determinism and indeterminism

Determinism in science had its origin in the philosophical musing of the French polymath Ren Descartes. According to his 1644 Principles of Philosophy, the physical world is a deterministic machine, where events are the inevitable and necessary consequences of antecedent events. Descartes concept of scientific determinism was rationalised by the laws of motion and gravity postulated by Isaac Newton in 1687. Much to the delight of the determinists, the laws allow us, in principle, to calculate and predict with clockwork precision every outcome in nature, under all conditions, as long as we know enough about what are called initial conditions. Hence, Newtonian physics, also known as classical physics, was and still is considered by many thinkers to be the paragon of determinism. They even apotheosized classical physics to be the omniscience of God who encompasses all knowledge of the universe - past, present and future. Subsequent to Newton, the French mathematician and physicist Pierre-Simon Laplace, a believer in causal determinism, speculated in the introduction to his 1814 Essai Philosophique sur les Probabilits that if someone, since dubbed as Laplaces Demon, determined the entire history of the universe, down to the last detail, then both the future and the past would hold no secrets whatsoever. This implies that the Universe, since its creation 13.7 billion years ago, is a gigantic clock, unwinding relentlessly along a rigid, pre-determined pathway towards an unalterable final state. In the first decade of the 20th Century, nature had a surprise in store for the determinists. They saw their world subverted when several studies of subatomic particles exposed many phenomena that couldnt be satisfactorily explained within the framework of deterministic classical physics. Determinism became irrelevant after physicists developed quantum mechanics to study the subatomic world. It casts reasonable doubt on the traditional determinism of classical physics by offering us a unique way of studying the structure of the physical universe in a way that was undreamt of in Newtons days. Unlike classical physics, quantum mechanics makes a clear-cut distinction between what can be known in principle and what is actually known by observation. This is manifested in Werner Heisenbergs famous uncertainty principle, which states that we cannot measure the position and momentum of subatomic particles simultaneously with arbitrarily high precision. As the cornerstone of quantum mechanics, the principle assures us that theres always an irreducible indeterminism in the operation of subatomic systems, thereby, rendering the concept of determinism in science irrelevant. Moreover, the basic principles of quantum mechanics tell us that nature is inherently unpredictable. As an example, we dont know how an electron in an excited state knows to which lower energy state it should jump, or when to jump. In fact, the electron doesnt know anything about itself a priori. Neither does quantum mechanics, it can only predict the probability of when and to which state the electron will jump. In other words, we cannot know exactly how something will turn out before it actually happens. The view that nature is governed by probability rather than certainty flustered Albert Einstein, a staunch believer in a deterministic universe. Despite being well aware that quantum mechanics had survived stringent experimental tests, he famously said, God doesnot play dice with the universe. Einstein maintained that if quantum mechanics were correct then the world would be crazy. According to him, God created Newtons laws of motion and the necessary masses and forces. That is all; everything else follows by deduction upon development of suitable mathematical methods. As for others who believe that events in the universe are fully predictable, without ambiguity or uncertainty, they recoiled at the idea that classical physics could no longer claim to predict the outcome of events with infinite precision. Nevertheless, in defense of classical physics, they argue that our inability to predict any more than probabilities is simply due to ignorance. Proponents of quantum indeterminacy, on the other hand, contend that the probabilistic nature of quantum mechanics is an inevitable consequence of the failure of causality in reality. Why were Einstein and other determinists troubled by a theory that works flawlessly? They were troubled not because quantum theory violates intuition and common sense. They were troubled because objects in quantum mechanics are neither particles nor waves, but a combination of both. They were troubled because quantum mechanics deals with ghostly, unobservable quantities, makes probability fundamental, and leaves the boundary between quantum realm and the realm of human perception quite vague. Most determinist eventually accepted the underlying uncertainty in quantum mechanics, albeit reluctantly. They, however, believe that theres probably a fundamental flaw in quantum mechanics that gives rise to indeterminism. Perhaps, theres some hidden variable that one day could allow them to predict things with perfect certainty again.They are still waiting for that one day. The remoteness of quantum phenomena from everyday experience may belie common sense. But we have to realise that physics of the past hundred years has taught us that common sense is a poor guide in the new realms of knowledge. It also taught us that science progresses by breaking the rules of the past. As we move from one level of reality to another in the study of nature, the laws and concepts used to describe it must change accordingly. n The writer is a Professor of Physics at Fordham University, New York. Photos: Google Images.