Imagine you're in a dream. In that dream, eating a certain substance causes the dream to warp in funny ways. You could say this is a proof that the substance ca

Imagine you're in a dream. In that dream, eating a certain substance causes the dream to warp in funny ways. You could say this is a proof that the substance causes perception shift, but both the substance and the apparent world are being generated by something deeper. It is possible to know this directly (as in lucid dreaming). It may sound preposterous to suggest the same is happening here, but it's the best analogy I can think of.