John Calvin challenges us with these opening words in his magisterial work,  Institutes of the Christian Religion:

The whole sum of our wisdom – wisdom, that is, which deserves to be called true and assured – broadly consist of two parts, knowledge of God and knowledge of ourselves….

[W]e observe that no one ever attains clear knowledge of self unless he has first gazed upon the face of the Lord, and then turns back to look upon himself. Deeply rooted in al of us is an arrogance which persuades us that we are righteous, truthful, wise and holy. Only clear evidence that we are unrighteous, deceitful, foolish and vile will convince us to the contrary…And because there is nothing around us which is not greatly defiled, whatever is a little less grubby appears to us a purity itself, as long as we confine our attention to the limits of our own – debased – humanity. It is like the eye which, used to seeing only objects that are dark, judges things which are vaguely white or even semi-grey to be the whitest there is.

An analogy based on physical sight will help us better understand how badly we misjudge our soul’s powers. If in broad daylight we look down at the ground or attend to things which are round about us, we have no trouble believing our sight is extremely sharp and keen. When, however, we look straight up at the sun, the power that served us so well on earth is dazed and dazzled by so intense a light, forcing us to admit that our ability clearly to see earthly objects is weak and feeble when it comes to gazing at the sun. This is how it is when we estimate our own spiritual thoughts. As long as we do not look beyond earth’s horizons, we are perfectly content with our righteousness, wisdom and power.

We flatter and congratulate ourselves, are not far from thinking we are demigods! If, however, we turn our thoughts toward the Lord and realize how consummate is his righteousness, wisdom and power which are the stand to which we must conform, what we once took to be righteousness will appear foul and utterly evil…indeed, what we reckon to be perfectly blameless in us will never match the purity to be found in God.