The thesis that aesthetic testimony cannot provide aesthetic justification or knowledge is widely accepted–even by realists about aesthetic properties and values. This Kantian position is mistaken. Some testimony about beauty and artistic value can provide a degree of aesthetic justification and, perhaps, even knowledge. That is, there are cases in which one can be justified in making an aesthetic judgment purely on the basis of someone else's testimony. But widespread aesthetic unreliability creates a problem for much aesthetic testimony. Hence, most testimony about art does not have much epistemic value. The situation is somewhat different with respect to aesthetic testimony about nature, proofs, and theories.

And yet he realizes clearly that other people's approval in no way provides him with a valid proof by which to judge beauty; even though others may perhaps see and observe for him, and even though what many have seen the same way may serve him, who believes he saw it differently, as a sufficient basis of proof for a theoretical and hence logical judgment, yet the fact that others have liked something can never serve him as a basis for an aesthetic judgment.

Immanuel Kant, Critique of Judgment