Why "integrity" means "honesty"
The word integrity meaning wholeness seems to come from the word integer which, roughly speaking, refers to whole numbers. Why does integrity also mean honesty?
Solution 1:
Dishonesty and other vices are often seen as corruptions, or shortcomings in a person's character or composition. An integral person, on the other hand, is whole. Such a person is not lacking in moral virtues.
Solution 2:
Etymology online has the following entry for integrity:
mid-15c., "wholeness, perfect condition," from O.Fr. integrité, from L. integritatem (nom. integritas) "soundness, wholeness," from integer "whole" (see integer). Sense of "uncorrupted virtue" is from 1540s.
That doesn't answer why integrity also means honesty, but you can see that circa 1540 the word began being used to express "uncorrupted virtue," which implies honesty, as a virtuous person does not lie.
Solution 3:
I'm not sure that integrity and honesty are entirely synonymous.
I think integrity is closer to the word consistent than the word honest. Of course, you couldn't really be dishonest and have integrity because dishonesty requires inconsistency between your words and your thoughts.
Solution 4:
I agree with @John Weldon that integrity and honesty aren't synonymous.
So defining integrity becomes important, and I'm inclined to go with the crowd on that--integrity in a human being is a state of having all the important virtues. Being "whole" or "complete" as a being of virtue. There would probably be some disagreement about which virtues are required for integrity, of course.
In this view, honesty can be seen as a necessary condition of integrity--you can't be "integrated" without it--but you can be honest and still lack integrity if you also lack other crucial virtues.
I think people sometimes think of integrity as synonymous with honesty because it's one of the most obvious virtues, and one that most people can agree is necessary for integrity.
Solution 5:
In the usage where integrity means honesty, it comes from a meaning that what you communicate and your actions/intentions are coherent with each other, forming a whole that has the property of integrity.