The phrase "ignorance is a soul" is most famously associated with the poet William Blake.

William Blake used the phrase to convey complex ideas:

• Spiritual Death: He saw ignorance not merely as a lack of knowledge, but as a state that deadens the spirit and prevents true understanding.
• Loss of Innocence: Ignorance, particularly when imposed or self-inflicted, can represent a corruption of the original, innocent state of being.
• Moral and Intellectual Stagnation: It traps people in limited perspectives, hindering growth and the ability to perceive truth.
• Source: The William Blake Archive

Ultimately, the meaning is open to interpretation, depending on the specific context in which Blake used the phrase.