John Calvin begins the Institutes of the Christian Religion, his 1500 page magnum opus, with the topic of knowledge of God and knowledge of self. The very fact Calvin would begin his entire work this way signifies its importance. As you read the Institutes it is easy to see the magnitude of this topic as it is constantly referenced throughout the rest of the book.
Why is this topic important? Because without a proper knowledge of self there can be no knowledge of God. In short, without a correct understanding of our own depravity and corruption we cannot aspire, nor would we ever be aroused, to seek God.
Likewise, without a proper knowledge of God there can be no knowledge of self. As long as we fail to see God for who He truly is, in all His majesty, we will never recognize or scrutinize our own lowly state but rather will continue to view ourselves in our natural fallen condition as "basically good."
All quotes are from the Battles translation, edited by John T. McNeill. Enjoy!
John Calvin on Spiritual Warfare
John Calvin on Total Depravity
JOHN CALVIN: KNOWLEDGE OF GOD, KNOWLEDGE OF SELF
1.1.1 Without knowledge of self there is no knowledge of God
Nearly all the wisdom we possess, that is to say, true and sound wisdom, consists of two parts: the knowledge of God and of ourselves. But, while joined by many bonds, which one precedes and brings forth the other is not easy to discern.
Thus, from the feeling of our own ignorance, vanity, poverty, infirmity, and - what is more - depravity and corruption, we recognize that the true light of wisdom, sound virtue, full abundance of every good, and purity of righteousness rest in the Lord alone... we cannot seriously aspire to him before we begin to become displeased with ourselves.
Accordingly, the knowledge of ourselves not only arouses us to seek God, but also, as it were, leads us by the hand to find him.
1.1.2 Without knowledge of God there is no knowledge of self
Again, it is certain that man never achieves a clear knowledge of himself unless he has first looked upon God's face, and then descends from contemplating him to scrutinize himself. For we always seem to ourselves righteous and upright and wise and holy-this pride is innate in all of us-unless by clear proofs we stand convinced of our own unrighteousness, foulness, folly, and impurity. Moreover, we are not thus convinced if we look merely to ourselves and not also to the Lord, who is the sole standard by which this judgment must be measured. For, because all of us are inclined by nature to hypocrisy, a kind of empty image of righteousness in place of righteousness itself abundantly satisfies us. And because nothing appears within or around us that has not been contaminated by great immorality, what is a little less vile pleases us as a thing most pure-so long as we confine our minds within the limits of human corruption.
As long as we do not look beyond the earth, being quite content with our own righteousness, wisdom, and virtue, we flatter ourselves most sweetly, and fancy ourselves all but demigods. Suppose we but once begin to raise our thoughts to God, and to ponder his nature, and how completely perfect are his righteousness, wisdom, and power-the straightedge to which we must be shaped. Then, what masquerading earlier as righteousness was pleasing in us will soon grow filthy in its consummate wickedness.
That is, what in us seems perfection itself corresponds ill to the purity of God.
1.1.3 Man before God's majesty
As a consequence, we must infer that man is never sufficiently touched and affected by the awareness of his lowly state until he has compared himself with God's majesty.
Yet, however the knowledge of God and of ourselves may be mutually connected, the order of right teaching requires that we discuss the former first, then proceed afterward to treat the latter.