What does the poet mean by not fool?

The poet, Percy Bysshe Shelley, means by "not fool" that the true poet is not a fool, but rather someone who is wise and has a deep understanding of the world. The poet is not someone who is easily deceived or fooled, but rather someone who is able to see through the surface of things and understand the deeper truths. The poet is someone who is able to see the beauty and wonder in the world, and who is able to express this beauty and wonder in their poetry.