Blake didn't simply prefer innocence. Both states are necessary; neither alone is complete. Innocence without experience is naive; experience without innocence becomes cynical. True vision requires "seeing through the eye, not with it"—perceiving both states simultaneously.
The famous pairing of "The Lamb" (Innocence) and "The Tyger" (Experience) illustrates this. The Lamb embodies gentleness and divine benevolence; The Tyger, with its "fearful symmetry," questions how the same creator made both. "Did he who made the Lamb make thee?" Blake doesn't answer but holds the tension.
Blake's "contrary states" anticipate dialectical thinking and depth psychology's recognition of psyche's multiplicity. He saw imagination as primary reality, the material world as diminished perception. His prophetic books develop complex mythologies exploring human fall and redemption.
Though considered mad by contemporaries, Blake profoundly influenced Romanticism and modernism. His insistence on seeing the infinite in the particular—"To see a World in a Grain of Sand"—represents visionary consciousness.
Source
Songs of Innocence and Experience - William Blake