Popper states that:

...There can be 2 incompatible theory, equally irrefutable; for example, determinism and his opposite, indeterminism.

Popper; Conjecture and Confutation chapter 8.

How can determinism not be a scientific theory, if we can clearly confutate it? For Popper determinism is:

"Future is conteined in the present, because is from it complitelly determined."

This theory is clearly confutable, since we just need one experiment that proves that in just one case something is not determined. Why he calls it a non-scientific theory?

  • 1
    There is no "just one case" with determinism, the universe does not split into causally isolated cases. Nor can we tell if a prediction of determinism came true or not. To prove that the future is not determined by the present we would have to first gather all the data about the present from all over the universe. Even then we can not be sure that we did not miss some law of nature that determines it even if we can't, or that our own actions aren't predetermined. And both our data and our measurements aren't infinitely precise, so that there is always a chance that we messed up.
    – Conifold
    Commented Jun 20, 2019 at 23:39
  • @Conifold What I'm asking is whether It is a scientific theory or not. Determinism means "everything is determined", so to confutate it you need 1 case in which 1 event was not determined by something, but was completely casual. From a logical point of view this theory can be falisified as much as the theory "every single man is taller that a mountain", and it's equally scientific. Moreover, what i got from Popper, i might be wrong, is that what he means by refutable is "logically refutable"; you need to controll an infinite number of cases to demonstrate something, but u need onli one to Commented Jun 21, 2019 at 9:26
  • @Conifold refutate he theory. The problem of stumentation never came to my attention for now in Popper's books, but i think that if something is not refutable because of the lack of precision in the instruments or of our current knowledge, then nothing at all can be refutate, so even einstein theories are not scientific, because we are not able to surelly refutate them due to the imprecision of our instruments... Commented Jun 21, 2019 at 9:30
  • No, determinism is not a scientific theory, it is a metaphysical doctrine. But there can be scientific theories that are deterministic, classical mechanics was one, so it can be used as a guideline for developing new theories. The difference is that classical mechanics made specific predictions about specific outcomes, whereas determinism in general is so vague that it can be made compatible with any outcome. It is true that just one negative outcome can falsify a theory, but there is no possible way to get one with determinism. "Everything is determined" predicts nothing in particular
    – Conifold
    Commented Jun 21, 2019 at 9:38
  • @Conifold Well we could say that it predicts a lot. It predicts that if u have an event A, that event had surelly a cause B. And this is true for every singol event in the universe. Probably the point is that you cannot experiment the quality of determination, and surelly u cannot know for sure that it was not determined by something u don't know. Commented Jun 21, 2019 at 9:51

1 Answer 1


You cannot know in any given experiment that something was not determined, only that it was not determined by the set of rules proposed.

So to run your experiment you would need a perfect set of rules.

This set of predictive rules would correctly predict all outcomes that can be predicted.

But then the set of rules already decided whether there is or is not determinism.

Say it decides there is determinism.

Then the test case cannot defy the rules, or they have failed to be perfect.

So the rules should decide against determinism.

Then there is no point in running the experiment.

A test case is not a confutation if it agrees with the predicted outcome.

  • Nice explanation! Though I prefer the shorter pithier version before the last edit
    – Rushi
    Commented Jun 21, 2019 at 6:49
  • I thought about something like this after i wrote the question, tell me if it is correct. We cannot know if that event didn't seem determined because it was not determined or because it was determined by something that we don't know. Commented Jun 21, 2019 at 9:36

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