i think if the main thing is “hearing voices” this kind of thing is probably a good strategy, but there are lots of other probably worse symptoms of psychosis.
You identify objective metrics, and confirm that they're objective and useful over the course of several days / weeks in a variety of different mental states. For example: "everyone thinks The Cloud™ will solve their problems, even though it never has" -> mass insanity. "Everyone thinks the sun will rise tomorrow, because it always has" -> extrapolation / inductive reasoning (probably fine).
