Let us look into ourselves without flattery or blind self-love. It is not strange that we are so deluded in this matter, seeing none of us can avoid that pestilential self-indulgence, which, as Scripture proclaims, is naturally inherent in all: “Every way of a man is right in his own eyes,” says Solomon (Prov. 21:2). And again, “All the ways of a man are clean in his own eyes,” (Prov. 16:2).
What then? does this hallucination excuse him? No, indeed, as Solomon immediately adds, “The Lord weigheth the spirits;” that is, while man flatters himself by wearing an external mask of righteousness, the Lord weighs the hidden impurity of the heart in his balance. Seeing, therefore, that nothing is gained by such flattery, let us not voluntarily delude ourselves to our own destruction.
To examine ourselves properly, our conscience must be called to the judgment-seat of God. His light is necessary to disclose the secret recesses of wickedness which otherwise lie too deeply hid. Then only shall we clearly perceive what the value of our works is; that man, so far from being just before God, is but rottenness and a worm, abominable and vain, drinking in “iniquity like water.” For “who can bring a clean thing out of an unclean? not one,” (Job 14:5). Then we shall experience the truth of what Job said of himself: “If I justify myself, mine own mouth shall condemn me: if I say I am perfect, it shall prove me perverse,” (Job 9:20).
Nor does the complaint which the prophet made concerning Israel apply to one age only. It is true of every age, that “all we like sheep have gone astray; we have turned every one to his own way,” (Isaiah 53:6). Indeed, he there comprehends all to whom the gift of redemption was to come.
And the strictness of the examination ought to be continued until it have completely alarmed us, and in that way prepared us for receiving the grace of Christ. For he is deceived who thinks himself capable of enjoying it, until he have laid aside all loftiness of mind. There is a well-known declaration, “God resisteth the proud, but giveth grace to the humble,” (1 Pet. 5:5).
So Calvin in the Institutes. Doing what ‘we’ think is right as opposed to doing what God says is right and deluding ourselves into believing that we are nonetheless ‘upright’ or ‘good’ is the surest sign not only of self delusion, but madness.