The whole point of art (creative activities for the purpose of other peoples' consumption) is for communication. When you experience some art, if it is good, you are basically forming a bond of trust with the creator which allows you to consider what they express as being more likely than chance to be truthful. The first task is to establish that trust, for instance by proving they have some naturally elevated level of insight, or they have some unusual experience. Art also has purely aesthetic purposes, but this is just a fulfillment of base (monkey-brain) desire which is MOSTLY achieved better by things that exist in real life anyway. The main exception is for some sense of "structural" aesthetics, where elements fit together in a satisfying pattern. This also shows up in mathematical proofs and other places. People have made attempts to express conscious-level truths ("philosophical") too, but this is just inefficient. It could work to serve the aforementioned purposes, though.