Leo the Great

But because "all men have not faith" and the crafty Tempter never delights so much in wounding the hearts of men as when he can poison their unwary minds with errors that are opposed to Gospel Truth, we must strive by the mighty teaching of the Holy Ghost to prevent Christian knowledge from being perverted by the devil's falsehoods. And against this danger it behoves the rulers of the churches especially to guard and to avert from the minds of simple folk lies which are coloured by a certain show of truth.