Most errors consist only in our not rightly applying names to things. For when someone says that the lines which are drawn from the center of a circle to its circumference are unequal, he surely understands (then at least) by a circle something different from what mathematicians understand. Similarly, when men err in calculating they have certain numbers in their mind and different ones on the paper. So if you consider what they have in mind, they really do not err, though they seem to err because we think they have in their mind the numbers which are on the paper. If this were not so, we would not believe that they were erring, just as I did not believe that he was erring whom I recently heard cry out that his courtyard had flown into his neighbor's hen, because what he had in mind seemed sufficiently clear to me. And most controversies have arisen from this, that men do not rightly explain their own mind, or interpret the mind of the other man badly. For really, when they contradict one another most vehemently, they either have the same thoughts, or they are thinking of different things, so that what they think are errors and absurdities in the other are not.

Ethics