Before Alan Turing made his crucial contributions to the theory of computation, he studied the question of whether quantum mechanics could throw light on the nature of free will. This paper investigates the roles of quantum mechanics and computation in free will. Although quantum mechanics implies that events are intrinsically unpredictable, the 'pure stochasticity' of quantum mechanics adds randomness only to decision-making processes, not freedom. By contrast, the theory of computation implies that, even when our decisions arise from a completely deterministic decision-making process, the outcomes of that process can be intrinsically unpredictable, even to-especially to-ourselves. I argue that this intrinsic computational unpredictability of the decision-making process is what gives rise to our impression that we possess free will. Finally, I propose a 'Turing test' for free will: a decision-maker who passes this test will tend to believe that he, she, or it possesses free will, whether the world is deterministic or not.
Before Alan Turing made his crucial contributions to the theory of computation, he studied the question of whether quantum mechanics could throw light on the nature of free will. This paper investigates the roles of quantum mechanics and computation in free will. Although quantum mechanics implies that events are intrinsically unpredictable, the 'pure stochasticity' of quantum mechanics adds randomness only to decision-making processes, not freedom. By contrast, the theory of computation implies that, even when our decisions arise from a completely deterministic decision-making process, the outcomes of that process can be intrinsically unpredictable, even to-especially to-ourselves. I argue that this intrinsic computational unpredictability of the decision-making process is what gives rise to our impression that we possess free will. Finally, I propose a 'Turing test' for free will: a decision-maker who passes this test will tend to believe that he, she, or it possesses free will, whether the world is deterministic or not.
In honor of Alan Turing's hundredth birthday, I unwisely set out some thoughts about one of Turing's obsessions throughout his life, the question of physics and free will. I focus relatively narrowly on a notion that I call ‘Knightian freedom’: a certain kind of in-principle physical unpredictability that goes beyond probabilistic unpredictability. Other, more metaphysical, aspects of free will I regard as possibly outside the scope of science. I examine a viewpoint, suggested independently by Carl Hoefer, Cristi Stoica, and even Turing himself, that tries to find scope for ‘freedom’ in the universe's boundary conditions rather than in the dynamical laws. Taking this viewpoint seriously leads to many interesting conceptual problems. I investigate how far one can go toward solving those problems and, along the way, I encounter (among other things) the no-cloning theorem, the measurement problem, decoherence, chaos, the arrow of time, the holographic principle, Newcomb's paradox, Boltzmann brains, algorithmic information theory, and the common prior assumption. I also compare the viewpoint explored here with the more radical speculations of Roger Penrose. The result of all this is an unusual perspective on time, quantum mechanics, and causation, of which I myself remain skeptical but which has several appealing features. Among other things, it suggests interesting empirical questions in neuro-science, physics, and cosmology; and it takes a millennia-old philosophical debate into some underexplored territory. When I was a teenager, Alan Turing was at the top of my pantheon of scientific heroes, above even Darwin, Ramanujan, Einstein, and Feynman. Some of the reasons were obvious: the founding of computer science, the proof of the unsolvability of the Entscheidungsproblem, the breaking of the Nazi Enigma code, the unapologetic nerdiness and the near-martyrdom for human rights. But beyond the facts of his biography, I idolized Turing as an ‘ über-reductionist’: the scientist who had gone further than anyone before him to reveal the mechanistic nature of reality. Through his discovery of computational universality, as well as the Turing Test criterion for intelligence, Turing finally unmasked the pretensions of anyone who claimed there was anything more to mind, brain, or the physical world than the unfolding of an immense computation.
Abstract Advancements in neuroscience make the question of free will more pressing. Between physicalist positions, which largely deny free will, and libertarian views, which reject determinism, quantum mechanics initially appeared to offer a middle ground. Even though it was thought to depict a probabilistic reality allowing some degree of freedom in choices, quantum mechanics remains deterministic, albeit with stochastic results. This paper proposes an alternative where quantum mechanics still supports free will as the possibility to do otherwise within a physicalist framework. Through the manyworlds interpretation, I show how the principle of alternative possibilities can be maintained, even when both our decision-making processes and the external world follow physical laws.
The question of human free will has remained a central philosophical challenge for millennia. In physics, the issue of determinism versus indeterminism resurfaces in quantum mechanics, where measurement choices play a key role. In this work, we propose an experimental protocol inspired by delayed-choice quantum eraser experiments, in which the random switching of measurement settings is not performed by a quantum random number generator (QRNG), but instead by human participants making rapid spontaneous choices. If human choices are fundamentally unpredictable in a way that is not reducible to quantum mechanics or physical determinism, then the universal wave function could not have encoded them prior to the decision event. By introducing quantum memories to extend the decision window and ensuring strict separation and blindness of participants, this experiment could test whether interference patterns depend on genuinely free human choices or yield results identical to QRNG-based protocols.
The question of human free will has remained a central philosophical challenge for millennia. In physics, the issue of determinism versus indeterminism resurfaces in quantum mechanics, where measurement choices play a key role. In this work, we propose an experimental protocol inspired by delayed-choice quantum eraser experiments, in which the random switching of measurement settings is not performed by a quantum random number generator (QRNG), but instead by human participants making rapid spontaneous choices. If human choices are fundamentally unpredictable in a way that is not reducible to quantum mechanics or physical determinism, then the universal wave function could not have encoded them prior to the decision event. By introducing quantum memories to extend the decision window and ensuring strict separation and blindness of participants, this experiment could test whether interference patterns depend on genuinely free human choices or yield results identical to QRNG-based protocols.
The question of human free will has remained a central philosophi- cal challenge for millennia. In physics, the issue of determinism versus indeterminism resurfaces in quantum mechanics, where measurement choices play a key role. In this work, we propose an experimental pro- tocol inspired by delayed-choice quantum eraser experiments, in which the random switching of measurement settings is not performed by a quantum random number generator (QRNG), but instead by human participants making rapid spontaneous choices. If human choices are fundamentally unpredictable in a way that is not reducible to quantum determinism, then the universal wave function could not have encoded them prior to the decision event. By introducing quantum memories to extend the decision window and ensuring strict separation and blind- ness of participants, this experiment could test whether interference patterns depend on genuinely free human choices or behave identically to QRNG-based protocols. A violation of standard quantum predic- tions would have profound consequences for physics, philosophy, and neuroscience.
Both deterministic and indeterministic physical laws are incompatible with control by genuine (non-illusory) free will. We propose that an indeterministic dynamics can be weakly compatible with free will (FW), whereby the latter acts by altering the probability distribution over allowed outcomes. In the quantum physical world, such a FW can collapse the wave function, introducing deviations from the Born rule. In principle, this deviation would stand in conflict with both special relativity and (a variant of) the Strong Church-Turing thesis, implying that the brain may be an arena of exotic, non-standard physics. However, in practice, these deviations would not be directly or easily observable, because they occur in sub-neuronal superpositions in the brain, where they would be shrouded in random measurement errors, noise and statistical fluctuations. Our result elucidates the difference between the FW of human observers and that of observed particles in the Free Will Theorem. This difference is a basic reason for why FW (and, in general, consciousness) cannot be recreated by standard artificial intelligence (AI) technology. We propose various neurobiological experiments to test our proposed theory. We speculate that for observers to be aware of a physical theory such as quantum mechanics, FW is necessary and that the theory must therefore not be universal. We suggest that FW may be regarded as a primitive principle in Nature for explaining quantum indeterminism.