There is not anything in the history of mankind more surprising, or at first view more unaccountable, than the self-partiality which prevails in the world. One would be apt to imagine, that it should not be so difficult to arrive at the knowledge of our real character, possessing, as we do, every possible advantage for attaining it.
Here then, is one striking evidence of the deceitfulness of the heart. It produces ignorance of ourselves; it keeps men strangers to their own character; and makes them fatally presume that they are in friendship with God, while they are enemies to him in their minds and by wicked works.
2) The deceitfulness of the heart appears from men's general disposition on all occasions to justify their own conduct.
….Because they are not chargeable with single determinate acts of gross wickedness, because you cannot precisely point out to them, in so many words, wherein they have done amiss, they falsely conclude, that their conduct is unexceptionable; though, perhaps, their general temper and behavior may be uniformly wrong, inconsistent with the spirit of the gospel, and contrary to the plainest dictates of morality. I proceed to observe,
3) That the deceitfulness of the heart appears from the difficulty with which men are brought to acknowledge their faults, even when conscious that they have done wrong.
But through the deceitfulness of the heart, men are generally disposed to justify their own conduct, and ready to throw the blame of what is amiss on anything else, "sooner than on themselves.
4) The deceitfulness of the heart appears from the disposition which men discover to rest in mere notions and forms of religion, while they are destitute of its power.
Hypocrisy in all its forms and appearances flows from the deceitfulness of the heart; for in general men deceive themselves, before they attempt to deceive others. Few are so bold as to lay down a plan of imposing on the world, without endeavoring, in the first instance at least, to impose on their own minds. Nor is it difficult, when the mind is strongly biased by the love of any particular sin, or the pursuit of any particular interest, to persuade ourselves that our conduct is, at least, excusable, if not innocent. A dishonest mind is satisfied with the basest shifts and evasions! And people who wish to be deceived into a good opinion of their conduct, are seldom at a loss to accomplish their purpose.
5) That the deceitfulness of the heart appears in the highest degree, when men overlook the real motives of their conduct, and mistake the workings of their own corruptions, "for the fruits of the Spirit of God.
Let us consider our conduct, not in the light in which self-love and self-partiality would present it to our minds, but in the light in which any impartial spectator would view it, in the light in which God's word teaches us to consider it, and in the light in which it will be judged of at last, when God shall bring to light the hidden things of darkness, and make manifest the counsels of all hearts.
We are all more or less liable to self-deceit; and those who think they have the least of it, are in general most of all under its dominion. Let us therefore distrust our own judgment, and, sensible of our own ignorance and liableness to mistake, let us pray to God for his divine teaching; saying, with Elihu in the book of job, 'That which I see not, teach me'; and with the Psalmist, 'Search me, O God, and know my heart; try me, and know my thoughts, and see if there be any wicked way in me, and lead me in the way everlasting.