© Michael Lacewing Determinism: varieties Michael Lacewing

Determinism defined Syllabus: ‘the belief that a determinate set of conditions can only produce one possible outcome given fixed laws of nature’ Universal causation: every event – everything that happens or occurs – has a cause –Even if we don’t know the cause, we don’t allow that something ‘just happened’ Causal necessity: given the total set of conditions under which the cause occurs, only one effect is possible

Causal necessity Regularity: the same cause will operate in the same way on different occasions (laws of nature) If the usual effect fails to follow, there must be something different about the situation We need to consider anything that could have an effect. The situation in which effect must follow cause is the entire state of the universe at that moment.

Physical determinism Everything that happens in the physical universe is causally determined by the state of the universe + laws of nature. –E.g. every decision is determined by the previous state of my brain If we could know the position of every particle in the universe + the laws of nature, every future physical event could be predicted in principle. –E.g. every movement of your body

Prediction and freedom Being able to predict what someone will do isn’t enough to show that they aren’t free. –Preferences –Character traits It depends on whether the basis for prediction rules out the possibility that a different action can’t happen.

Hard determinism and libertarianism Agree: If physical determinism is true, we do not have free will. Hard determinism: Physical determinism is true. Therefore, we do not have free will. Libertarianism: We have free will. Therefore, physical determinism is false.

Chance and determinism Chaos theory: a tiny change in cause can have a big effect –This is not only compatible with determinism, it depends on it! Quantum mechanics –Theory about sub-atomic particles –Some believe there is genuine randomness at this level, or that quantum states are not determinate –E.g. Heisenberg’s Uncertainty Principle: you cannot accurately measure the velocity and position of an electron simultaneously - is this because it doesn’t have a precise velocity/position until measured?

Chance and determinism Other physicists reject indeterminacy as ‘out there’; Schrodinger’s equation shows that sub-atomic states change with perfect regularity Some say that the randomness and indeterminacy reflects limitations on our knowledge In any case, quantum indeterminacy does not affect the supra-atomic level