On Christian Doctrine

5. But because words pass away as soon as they strike upon the air, and last no longer than their sound, men have by means of letters formed signs of words. Thus the sounds of the voice are made visible to the eye, not of course as sounds, but by means of certain signs. It has been found impossible, however, to make those signs common to all nations owing to the sin of discord among men, which springs from every man trying to snatch the chief place for himself. And that celebrated tower which was built to reach to heaven was an indication of this arrogance of spirit; and the ungodly men concerned in it justly earned the punishment of having not their minds only, but their tongues besides, thrown into confusion and discordance.