The answer to the free will/determinism problem is not binary; it's not either/or, but traditionally it has been heavily skewed towards determinism by materialist philosophers.
A good starting point for the deterministic view was posited by French polymath Pierre-Simon Laplace in A Philosophical Essay on Probabilities (1814). Imagine a superintelligence that knows the precise location and momentum of every single atom in the universe. From that knowledge, it can calculate their past and future values according to the laws of classical mechanics – from the beginning of time to the end of time. So everything is predetermined. "For such an intellect nothing would be uncertain and the future just like the past could be present before its eyes," he wrote. Later named 'Laplace's Demon', this became a famous thought experiment that seemingly dismisses free will.
Note, however, that term 'classical mechanics'.
Because as soon as quantum mechanics appeared on the scene, around 100 years ago, the uncertainty principle at its heart would shake determinism to its classical core. Is that photon a particle or a wave? When will that atom of radioactive isotope decay? Is Schrodinger's Cat dead or alive? At the subatomic level, uncertainty rules. Quantum mechanics is probabilistic in nature. Faced now with an quantum universe, Laplace's Demon becomes unable to answer with certainty what will happen within an atom a fraction of a second into the future, let alone what will happen to you in a ten years' time.
Physicalist science and classical mechanics still work at our observable level, but this is no longer good enough to render an accurate picture of reality. "Who cares about the subatomic?" you may ask. It has implications.
Quantum mechanics can define the properties of ensembles of particles – but not individual ones. Predicting the exact outcome for a single particle is impossible. However, the theory can predict the probabilistic behaviour of a large number of particles; the larger, the more accurate. And in our day-to-day human-scale reality, quantum mechanics demonstrates remarkable agreement with experimental observations, extending to a great many decimal places.
This predictive power does allow scientists to make precise calculations in various domains, including electronics. Understanding how electrons behave in solids, a key concept in quantum mechanics, was fundamental to developing semiconductor theory, for example. Without this knowledge, the progress that we've seen in transistors, the backbone of modern computers – and indeed all modern electronics – would have been held back. Our computers would likely still be relying on vacuum tubes, slow and bulky.
Yet despite quantum mechanics' success in prediction, the underlying reality it describes remains philosophically puzzling. We understand the mathematical framework, but the dead cat? A hundred years on, there's no consensus as to which interpretation of quantum mechanics is most accurate. The theory is counterintuitive and challenges our classical understanding of the world.
So the three key aspects of quantum mechanics we need to grasp are:
- Wave-particle duality: particles can exhibit wave-like behavior, and vice versa, defying the classical distinction between the two.
- Superposition: a quantum system can exist in multiple states simultaneously, until it is observed, which seems contrary to everyday experience.
- Entanglement: two particles can become linked in a way that their fates are intertwined, regardless of the distance separating them, seemingly defying the concept of locality.
These concepts have led to various interpretations of quantum mechanics. Wikipedia lists 13 mainstream interpretations, and numerous unorthodox interpretations. Each one attempts to explain what's going on behind the mathematical framework. None has gained universal acceptance. This lack of consensus reflects the ongoing debate about the philosophical implications and ontological meaning of the theory.
And so, we don't know what reality truly looks like at the quantum level, at which deterministic classical mechanics holds no sway.
In particular, is the presence of a conscious observer necessary to determine whether a photon is a wave or a particle, or which state a quantum system is in, or that one entangled particle behaves in a way linked to its twin's behaviour?
What is the role of consciousness in this quantum world? Can it therefore influence outcomes? And if it can – what does this mean for the notion of free will?
I would argue that there's a spiritual dimension to the question also. Your biological body may indeed be far less free than your ego might suppose, shaped by the determinism of classical-mechanical reality, but the consciousness experienced within your mind has far a greater range of options.
More tomorrow.
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