Causal Determinism is the concept that events are bounded by causality in such a way that any state (of an object or event) is completely determined by prior states.

The Principle of Sufficient Reason states that everything must have a cause or reason.

Is there a relationship between these two concepts? Does one imply the other?

2 Answers 2


Nothing implies causal determinism. It is just a theoretical idea.

Principle of sufficient reason has nothing to do with determinism. While determinism assumes that prior events only are both sufficient and necessary reasons for everything, the principle does not make that assumption.

Determinism assumes that prior events sufficiently determine their effects with absolute accuracy. In reality, there is probabilistic inaccuracy in all events. The effect is only partially determined by the cause.

Determinism assumes that prior events are the necessary reason for everything. The principle does not require past events. The reason can also be a purpose in the future. Voluntary actions are done for a purpose instead of due to a cause.


Hard determinism is a view on free will which holds that determinism is true and further it is incompatible with free will, and therefore that free will does not exist. So hard determinism is not equivalent or entailed by Principle of Sufficient Reason (PSR). PSR may very well imply soft determinism(Compatibilism) or even indeterminism. PSR is a more general metaphysical principle.

  • Thank you for clarifying my definition... I had hard determinism confused with causal determinism... I got my incorrect definition of hard determinism from this popular video by Crash Course Philosophy: youtube.com/watch?v=vCGtkDzELAI Jun 3, 2021 at 5:11
  • But could you clarify the distinction between Causal determinism and PSR? I feel they are related somehow... Jun 3, 2021 at 5:28
  • @AnujManojShah they're related as you rightly conceived. In your PSR reference writes "In contingent truths, even though the predicate is in the subject, this can never be demonstrated, nor can a proposition ever be reduced to an equality or to an identity, but the resolution proceeds to infinity, God alone seeing". So PSR implies determinism only from God's eye, no human can prove it. In science, most specifically quantum physics, indeterminism is the belief that no event is certain and the entire outcome of anything is probabilistic. So if you adopt indeterminism doesn't mean PSR must fail. Jun 3, 2021 at 5:52
  • @DoubleKnot There are philosophers like Nozick who say the original PSR must fail in light of quantum mechanics (he focused on an interpretation where the wavefunction is complete - no more knowledge possible about the system); only a weakened version can survive. And I would say a similar thing for causal determinism using the same logic.
    – J Kusin
    Jun 3, 2021 at 15:34
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    @AnujManojShah indeed as you rightly conceived and confused Hume seems reject PSR from his famous problem of induction. But there Hume mainly opposed uniformity of conformity, causality as mere phenomenal constant conjunction from human being's capability. But Leibniz emphasized PSR exists (only God sees it all) but usually cannot be known by us human beings. So even if Hume is right, it doesn't mean PSR fails or causality doesn't exist at all logically. Jun 5, 2021 at 4:25

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