QuestionsAre we free?We are biological machines: free will is a convenient illusion
Are we free?No free will

We are biological machines: free will is a convenient illusion

Biological machines (Hawking)

Stephen Hawking 1942 · 2018A theoretical physicist who sees the origin of the universe in the laws of physics rather than in a creator.
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What it claims

We are no more than biological machines, and free will is just an illusion. We nevertheless go on speaking of free will as an 'effective theory', because we cannot calculate what a brain does.

Why

The brain follows physical laws like the planets: if our acts come from it, where could free will act?

The same idea through history
Pierre-Simon de Laplace1814Laplace imagines an intelligence that, knowing the state of the universe, could calculate the whole future: determinism comes from mechanics.Benjamin Libet1983Libet shows that the brain prepares the movement before the subject reports deciding: neurology replaces mechanics.
Stephen Hawking2010Hawking and Mlodinow draw the conclusion from physics and biology: we are 'biological machines'. Free will remains useful as an 'effective theory'.
In short

"We are biological machines: free will is a convenient illusion" is an argument by Stephen Hawking (Hawking and Mlodinow, The Grand Design, 2010, ch. 2, 2010) on the question "Are we free?" (answer: no free will). Its claim: We are no more than biological machines, and free will is just an illusion. We nevertheless go on speaking of free will as an 'effective theory', because we cannot calculate what a brain does. According to AskPhilosophy's logic check (Z3 solver), the conclusion does follow from its 3 premises. AskPhilosophy presents 2 objections, 0 of them with a documented reply, and the original text behind each premise, checked word for word.

Hawking and Mlodinow, The Grand Design, 2010, ch. 2
Valid

In The Grand Design (2010), Hawking and Mlodinow raise the question of free will in connection with the laws of science. They start from biology: our cells, neurons and molecules follow physics and chemistry, as the planets follow their orbits. If our brain decides our acts, and the brain follows these laws, where could free will act? Their answer: nowhere. But they add that we cannot calculate what a brain does, so we speak of free will as a practical tool.

P1Biological processes follow the laws of physics and chemistry: they are as determined as the orbits of the planets.
P2It is our physical brain, following the known laws of science, that determines our actions, and not some agency existing outside those laws.
P3It is hard to imagine how free will could operate if our behaviour is determined by physical law.
So we are no more than biological machines, and free will is just an illusion. We nevertheless go on speaking of free will as an 'effective theory', because we cannot calculate what a brain does.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Valid. Hawking writes 'it seems that': the text does not claim a proof. The conclusion follows from the three premises if 'free will' means being able to act otherwise than physical law determines. The objections therefore bear on P2 (does neuroscience really show that the brain decides in our place?) and on the meaning of 'free will' (compatibilists say it fits with determinism).
Analogy. A weather forecast: we cannot calculate every drop, so we say 'it will rain'. Hawking compares free will to this kind of shortcut: useful for predicting, but not describing what really happens. The image is ours.

Objections

2

Each objection is a conversation: click to see who replies and where the debate stands.

David Hume (the compatibilists) 1748 · attacks the conclusion

Hume writes that by liberty we can only mean a power of acting or not acting according to the determinations of the will: if we choose to remain at rest we may; if we choose to move we may also. This liberty fits with necessary causes. Determinism therefore does not remove it, and the illusion Hawking describes is not one.

no reply
We have not yet found a direct reply by Hawking in the texts.
The debate goes on (our summary) Hawking does not discuss Hume in the passage we read. He does seem aware of it: he speaks of an effective theory in which people are said to have free will. A defender of Hawking would say Hume's liberty is too weak to count as free will, since the will itself is determined. A compatibilist would answer that it is the only liberty that matters for morality and law (our summary).
Where the debate stands (our summary)The core disagreement is over the term: does 'free will' mean being able to act on one's will, or being able to will otherwise? No agreement (our summary).
A
Aaron Schurger, Jacobo Sitt and Stanislas Dehaene 2012 · attacks premise 2

The neuroscientists Schurger, Sitt and Dehaene study the brain activity that precedes a voluntary movement, the 'readiness potential'. It was seen as the preparation of the decision. They propose another reading: it would mainly be spontaneous fluctuations in neuronal activity, which produce the movement when they cross a threshold. The activity before the movement therefore does not show that the brain has already decided.

no reply
We have not yet found a direct reply by Hawking in the texts.
The debate goes on (our summary) The paper appears two years after The Grand Design. We found no reply by Hawking. A defender of his thesis would say these fluctuations are also physical events in the brain: the result does not make the decision freer, only more random. It should be added that Hawking's examples are not the readiness potential but the stimulation of awake patients' brains: Schurger's paper reaches only part of the evidence invoked for P2 (our summary).
Where the debate stands (our summary)Open point: brain experiments do not settle the question of free will. They say what happens before a movement, not whether a decision is free (our summary).