I am also reading the fantastic From Dawn to Decadence: 500 Years of Western Cultural Life 1500 to the Presentby Jacques Barzun. On page 73 Barzun is talking about the 16th Century and the way perceptions of art were changing:
Aesthetic appreciation is something more than spontaneous liking; a good eye for accurate representation is not good enough; one must be able to judge and talk about style, technique, and originality. This demand gives rise to a new public character: the critic. The future professional begins by being simply the gifted art lover who compares, sees fine points, and works up a vocabulary for his perceptions. He and his kind are not theorists but connoisseurs and ultimately experts. [italics his]
A good definition of a critic, if a lot shorter than Bordwell's.