Calvin, from The Institutes, on how to gain (accurate) self-knowledge (emphasis mine):
“It is evident that man never attains to true self-knowledge until he has previously contemplated the face of God, and come down after such contemplation to look into himself. For (such is our innate pride) we always seem ourselves just, and upright, an wise, and holy, until we are convinced, by clear evidence, of our injustices, vileness, folly, and impurity. Convinced, however, we are not, if we look to ourselves only, and not to the Lord also – He being the only standard by the application of which this conviction can be produced. For, since we are naturally prone to hypocrisy, any empty semblance of righteousness is quite enough to satisfy us instead of righteousness itself.
In other words, if we want to understand ourselves correctly, we need to see ourselves in relationship to God, otherwise we will be prone to self-deception.
Also, for the Christian attempting to communicate the not-so-popular concept of “sin” – begin by communicating an accurate picture of God.
On an unrelated note, after quoting from Kuyper last week, and now Calvin, it is clear to me that somebody needs to hand me a book by Wesley!