For example, quantum mechanics presents a theory of how the universe works. But quantum mechanics is non-falsifiable. Stephen Weinberg (the father of the standard model of physics) says:
"Quantum mechanics is really an empty stage. It doesn’t tell you anything by itself. That’s why I think Karl Popper was wrong to say that a scientific theory must be open to falsification. You can’t falsify quantum mechanics, since it doesn’t make predictions. It’s a very general framework, one within which you can formulate theories that do make predictions. Newtonian physics isn’t formulated in quantum mechanics, but all our modern theories are. And quantum mechanics by itself does not say anything about the universe spontaneously coming into existence. For that sort of thing, you need quantum mechanics with other theories married to it.” (In Jim Holt, Why Does the World Exist?: An Existential Detective Story, pp. 157-158)
- The idea that a theory, to be epistemically reputable, must be falsifiable, is false.
- Therefore theism as a theory is not to be rejected should it be non-falsifiable. (I'm not certain this is true; viz., that theism is non-falsifiable. But it seems clear, following Weinberg, that mere non-falsifiability does not discredit a theory.)