Liberty of thought is the life of the soul.

The line frames freedom of thought as not merely a political right but an inner necessity: the mind’s ability to question, doubt, and judge for itself is what animates a person’s moral and intellectual life. Read in a broadly Voltairean key, it aligns with Enlightenment commitments to reason, toleration, and resistance to dogma—suggesting that coercing belief (by church or state) deadens the human spirit. The metaphor of “life of the soul” elevates intellectual liberty to a spiritual plane, implying that even material freedoms are hollow if one’s conscience and judgment are constrained.