Although we have already spoken in the First Part touching the utility of the definition of terms, it is nevertheless so important, that we cannot have it too much impressed on our minds, since we may by it clear up a number of disputes, which have as their subject often only the ambiguity of terms, which one takes in one sense, and another in another. So that some of the greatest controversies would cease in a moment, if one or the other of the disputants took care to make out precisely, and in a few words, what he understands by the terms which are the subject of dispute.

Antoine Arnauld (1612-1694) French theologian, philosopher, mathematician
Logic, or the Art of Thinking [La Logique ou l’art de penser; The Port-Royal Logic], Part 4, ch. 4 (1662) [with Pierre Nicole] [tr. Baynes (1850)]
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Alternate translation:

Although we have already spoken in Part I about the usefulness of defining one's terms, this is, however, so important that we cannot bear it too much in mind, since this is how countless disputes are cleared up whose cause is often merely an ambiguity in terms that one person takes one way and another person another way. Accordingly, some very serious arguments would cease in an instant if either of the disputants took the care to indicate clearly, in a few words, the meanings of the terms that are the subject of dispute.
[tr. Buroker (1996)]