Yet the most profound and penetrating of the causes that have transformed society is a medieval inheritance. It was late in the thirteenth century that the psychology of Conscience was closely studied for the first time, and men began to speak of it as the audible voice of God, that never misleads or fails, and that ought to be obeyed always, whether enlightened or darkened, right or wrong. The notion was restrained, on its appearance, by the practice of regarding opposition to Church power as equivalent to specific heresy, which depressed the secret monitor below the public and visible authority. With the decline of coercion the claim of Conscience rose, and the ground abandoned by the inquisitor was gained by the individual. There was less reason then for men to be cast of the same type; there was a more vigorous growth of independent character, and a conscious control over its formation. The knowledge of good and evil was not an exclusive and sublime prerogative assigned to states, or nations, or majorities. When it had been defined and recognised as something divine in human nature, its action was to limit power by causing the sovereign voice within to be heard above the expressed will and settled custom of surrounding men. By that hypothesis, the soul became more sacred than the state, because it receives light from above, as well as because its concerns are eternal, and out of all proportion with the common interests of government. That is the root from which liberty of Conscience was developed, and all other liberty needed to confine the sphere of power, in order that it may not challenge the supremacy of that which is highest and best in man.