The Enchiridion by St. Augustine
Chapter 21.--Error, Though Not Always a Sin, is Always an Evil.
But as to those matters in regard to which our belief or disbelief, and indeed their truth or supposed truth or falsity, are of no importance whatever, so far as attaining the kingdom of God is concerned: to make a mistake in such matters is not to be looked on as a sin, or at least as a very small and trifling sin. In short, a mistake in matters of this kind, whatever its nature and magnitude, does not relate to the way of approach to God, which is the faith of Christ that |worketh by love.| For the |mistake pleasing to parents| in the case of the twin children was no deviation from this way; nor did the Apostle Peter deviate from this way, when, thinking that he saw a vision, he so mistook one thing for another, that, till the angel who delivered him had departed from him, he did not distinguish the real objects among which he was moving from the visionary objects of a dream; nor did the patriarch Jacob deviate from this way, when he believed that his son, who was really alive, had been slain by a beast. In the case of these and other false impressions of the same kind, we are indeed deceived, but our faith in God remains secure. We go astray, but we do not leave the way that leads us to Him. But yet these errors, though they are not sinful, are to be reckoned among the evils of this life which is so far made subject to vanity, that we receive what is false as if it were true, reject what is true as if it were false, and cling to what is uncertain as if it were certain. And although they do not trench upon that true and certain faith through which we reach eternal blessedness, yet they have much to do with that misery in which we are now living. And assuredly, if we were now in the enjoyment of the true and perfect happiness that lies before us, we should not be subject to any deception through any sense, whether of body or of mind.