Determinism is the thesis that the state of the world at any moment, plus the laws of nature, fixes everything that happens afterwards.
Sir William Hamilton, 1846, in his notes to his edition of Thomas Reid's Works — the OED's earliest evidence. Before him the word for it was 'necessarian'.
// Where it sits
Not the same as unfree, and not the same as predictable. Three separate questions.
What it really means
Almost every argument about determinism goes wrong in the same place, and the Latin shows why. Dē- + terminus means to set the boundary of. The image is a fence, not a puppet string.
What gets substituted for it is fatalism — the idea that the outcome arrives whatever you do, that your struggling is decorative. These are cleanly separable. Fatalism bypasses your choices; determinism runs through them. Under determinism your deliberation is a genuine link in the causal chain, and removing it would change what happens. It simply also has causes of its own.
Two other confusions worth clearing. Determinism is not predictability. For any observer stuck inside the universe, one simply does not follow from the other — chaotic systems are perfectly deterministic and practically unforecastable, because a rounding error at the fourth decimal place becomes a hurricane. A determined universe can be permanently opaque to its own inhabitants.
And quantum mechanics has not settled this. The standard interpretations look indeterministic, but deterministic alternatives like Bohmian mechanics reproduce identical predictions, and the honest verdict is that current physics doesn't tell us whether determinism holds of our world.
Which leaves the question about free will genuinely open, and — notably — not automatically lost. Compatibilism holds that freedom is acting on your own reasons without external constraint, and that a chain of causes running through your reasons is not the same as a chain that goes around them.
Where it comes from
The literal Latin sense is 'to set the boundary of' — the picture is a fence, not a puppet string. That distinction is exactly what the fatalism confusion loses.
Myths & misconceptions
If determinism is true, nothing you do matters — it's all fated.
Fatalism is clearly separable from determinism. Fatalism says the outcome arrives whatever you do; determinism says your doing is one of the causes it arrives through. Under determinism your deliberation is a real link in the chain — it just has causes of its own.
A deterministic universe would be predictable in principle.
Not for anyone inside it. As the Stanford Encyclopedia of Philosophy puts it, when it comes to predictability of future events by finite agents in the world, predictability and determinism are 'simply not logically connected at all'. Chaotic systems are fully deterministic and practically unforecastable.
Compare & contrast
Determinism vs fatalism
Determinism grounds outcomes in prior states plus natural law; fatalism says you are powerless to do anything other than what you actually do, and the classical arguments for it run either on logical necessity or on the existence and nature of God, not on natural law. The practical difference is enormous — under determinism, deliberating changes the outcome, because the deliberation is part of the cause.
| // | Determinism | Fatalism |
|---|---|---|
| Outcome fixed by | Prior states + laws | Logical or theological necessity |
| Your choices | Are causes | Are bypassed |
| Deliberation matters | Yes | No |
| Requires the supernatural | No | Not necessarily — logical or theological |
How it connects
- Sisypheanboth raise the question of whether effort means anything when the outcome is set.
- Tabula Rasaboth concern how much of what you are was settled before you arrived.
Tell it apart
Questions people ask
- Does quantum physics disprove determinism?
- Not decisively. Standard interpretations of quantum mechanics look indeterministic, but deterministic alternatives such as Bohmian mechanics reproduce the same predictions. The Stanford Encyclopedia of Philosophy's assessment is that current theories carry unresolved puzzles, so this doesn't really tell us whether determinism is true of our world.
- What's the difference between determinism and fatalism?
- Determinism grounds outcomes in prior states plus natural law; fatalism says you are powerless to do otherwise, and its classic arguments run either on logical necessity or on the nature of God. Under determinism your deliberation is a real link in the causal chain — it just has causes of its own. The two are clearly separable.
- Can you have free will if determinism is true?
- Compatibilists say yes and redefine freedom as acting on your own reasons without external constraint. Hard determinists say no. Libertarians accept the incompatibility and reject determinism instead. Those three positions frame most of the debate, though they don't exhaust it.