How does Socrates distinguish knowledge known through art from knowledge known through inspiration?

Socrates characterizes artistic knowledge as universal. Therefore, one who knows the art of poetry could equally recite or analyze the poetry of any other poet. However, inspiration is a more enigmatic virtue of knowledge. Because Ion cannot recite any poet's poetry, he must have knowledge of poetry through divine inspiration. In short, Socrates separates the critics of art from the creators of art, where there former has less limitations on their craft but also less creative potential.