When does an economic theory become true? When does an economic theory become true?

When does it satisfy requirements for true knowledge, e.g. similar to those in empirical sciences?
It's just the same as in the physical sciences:

an economic theory, like any theory or model in physics or chemistry or biology, is wrong (H/T George Box), but it can be useful.

"True knowledge" is not a really a useful concept; not in physical sciences, not in social sciences. The important question is whether a model gives us useful insights, and whether it can constructively inform decisions.

An economic theory gains acceptance when it turns out to be useful.