Damascene Philosophy

QuestionsII

Is the future already fixed?

If the laws of physics plus the state of the universe settle everything that happens, then everything you will ever do was settled before you were born.

Reading time
4 min
Difficulty
Intermediate
Branch
Free will
First posed
Leucippus and Democritus, 5th century BCE; made precise by Pierre-Simon Laplace, 1814

The question

Drop a ball and it falls. Given its position, its speed and the forces acting on it, there is exactly one way it can move. Physics is the science of such necessities, and for centuries it seemed to apply to everything without exception.

Determinism is the thesis that this is true of the whole universe: the complete state of the world at any moment, together with the laws of nature, fixes the complete state of the world at every later moment. Not just planets and billiard balls, but weather, markets, conversations and the decision you will make about dinner.

If determinism is true, the future is not open in the way it feels. It is like the later pages of a book that has already been printed; you simply have not read them yet.

“We ought then to regard the present state of the universe as the effect of its anterior state and as the cause of the one which is to follow.”

Pierre-Simon Laplace, A Philosophical Essay on Probabilities (1814)

Why it matters

Determinism is the main pressure on free will. It is also central to science itself: the success of prediction depends on regularity, and many scientists treat 'everything has a cause' as a working assumption.

It matters, too, for how we think about luck, regret and blame. If a criminal's act was fixed by forces outside him, our attitude toward him may need to change. If your successes were fixed in the same way, so does your pride.

Key terms

  • DeterminismThe thesis that the state of the world at any moment, together with the laws of nature, fixes everything that happens afterwards.
  • FatalismThe view that what will happen will happen whatever we do, so that our choices make no difference to the outcome. Distinct from determinism, which says our choices are themselves causes.
  • IndeterminismThe thesis that not every event is fixed by prior events and the laws of nature; some involve genuine chance.
  • Laws of natureThe basic regularities, or the principles behind them, that govern how the physical world behaves, such as the conservation of energy.
  • CausationThe relation between a cause and its effect. Philosophers disagree about whether it is a real necessary connection or, as Hume argued, just regular succession that we have learned to expect.

The positions

Position I

Determinism is true

Every event is fixed by prior events and the laws of nature. Apparent randomness is only our ignorance.

Position II

Indeterminism is true

Some events, at least at the quantum level, are not fixed by what came before. The future is genuinely open.

Position III

The question is unsettled

Physics has not decided between deterministic and indeterministic interpretations, and may never be able to.

Arguments and objections

Determinism is true

Best argument
Science keeps finding causes where people once saw chance or spirit. Classical physics is deterministic, as is general relativity. Even quantum mechanics has deterministic interpretations, such as Bohmian mechanics and the many-worlds interpretation view, in which the underlying equation never stops being deterministic. Nothing we know forces us to give up the principle that every event has a sufficient cause.
Strongest objection
The standard reading of quantum mechanics says that some events, like the moment a radioactive atom decays, have no sufficient cause. They are governed by probabilities, not certainties. If that is right, determinism is false at the foundation of physics.
The reply
Determinists reply that the interpretation of quantum mechanics is unsettled, and that even if tiny events are random, their effects may average out at the scale of brains and bodies, leaving human behaviour effectively determined.

Indeterminism is true

Best argument
Our best-confirmed physical theory, quantum mechanics, in its most widely taught interpretation, describes outcomes that are irreducibly probabilistic. Experiments testing Bell's theorem have ruled out a broad class of hidden-variable theories that would restore determinism in a simple local way. We should follow the physics.
Strongest objection
Bell's results do not rule out all deterministic theories, only local ones; nonlocal and many-worlds approaches survive. And even if indeterminism is true, random fluctuations at the quantum level do not obviously give us the open future that matters for human choice.
The reply
Indeterminists accept that chance alone may not help free will, but argue that it at least removes the strongest argument against it, and leaves room for other accounts of agency.

The question is unsettled

Best argument
Different interpretations of quantum mechanics make the same predictions for every experiment performed so far. Whether the universe is deterministic may be a question that observation cannot settle, which suggests caution about building ethics or law on either answer.
Strongest objection
Agnosticism can become a way of avoiding a question that has real consequences. Some interpretations are simpler or better motivated than others, and we usually let such considerations guide belief.

Who argued what

Variations

Fatalism is not determinism

Fatalism says that what will be will be no matter what you do, as in the story of the man who flees to Samarra to escape Death, only to meet Death there. Determinism says something different: what you do is part of the causal chain. Your choices matter; they are just themselves caused.

Theological determinism

If an all-knowing God knows today what you will do tomorrow, can you do otherwise? Medieval thinkers from Augustine of Hippo to Boethius argued over whether divine foreknowledge leaves room for freedom, often by arguing that God stands outside time.

Go deeper

Chaos is not indeterminism

Chaotic systems, like the weather, are extremely sensitive to initial conditions: a tiny change can lead to a huge difference later. This makes them unpredictable in practice. But chaos is perfectly compatible with determinism. The weather may be fully fixed by its present state, even though no finite observer could ever measure that state precisely enough to predict it.

Determinism and prediction come apart

A deterministic universe need not be predictable from the inside. A predictor that is itself part of the universe may disturb what it measures, may lack the memory to model a system as complex as itself, or may face self-reference: announce a prediction about someone, and they can do the opposite. See Laplace's demon and Newcomb's problem.

Related ideas

Question

Is free will an illusion?

You feel like the author of your choices. The question is whether that feeling tracks anything real.

Thought experiment

Could a perfect mind predict everything?

Imagine an intellect that knows the position and motion of every particle. In a deterministic universe, nothing would be uncertain to it, and the future would be as plain as the past.

Question

Can you be free in a determined universe?

Perhaps freedom never meant escaping causes. Perhaps it means acting from your own reasons, which can be caused like anything else.

Question

Are there other versions of you?

On one serious reading of quantum mechanics, every possible outcome happens, each in its own branch of reality, with its own copy of you.

Question

Is time real?

Time feels like a river carrying us from past to future. Physics describes it more like a map, with no moving 'now' anywhere on it.

Further reading and sources

Open questions

  • If the future is fixed, is deliberation pointless, or is it simply one of the causes that fixes it?
  • Could we ever know, from inside the universe, whether it is deterministic?
  • Would randomness at the bottom of physics make you any freer?

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