  Finally, the “Main Principles” introduce a fourth source of perfection and therefore pleasure in the aesthetic experience, namely our appreciation of the artistry that is manifested in the production of a beautiful object. In explaining this source of pleasure, Mendelssohn also makes another revision to the traditional theory that it is resemblance alone that is the source of our pleasure in imitation, because resemblance is easily produced by means far less complex and admirable than all of the faculties that go into artistry—a point that Plato had already made when he had Socrates argue that if it is mere imitation that the painter were after, he could just go around with a mirror (Plato, Republic, Book X, 596d–e):