... unless we have some just idea of our hearts and of sin, we can have no right idea of a Moral Governor, a Saviour or a Sanctifier, that is, in professing to believe in Them, we shall be using words without attaching distinct meaning to them. Thus self-knowledge is at the root of all real religious knowledge; and it is in vain,—worse than vain,—it is a deceit and a mischief, to think to understand the Christian doctrines as a matter of course, merely by being taught by books, or by attending sermons, or by any outward means, however excellent, taken by themselves. For it is in proportion as we search our hearts and understand our own nature, that we understand what is meant by an Infinite Governor and Judge; in proportion as we comprehend the nature of disobedience and our actual sinfulness, that we feel what is the blessing of the removal of sin, redemption, pardon, sanctification, which otherwise are mere words. God speaks to us primarily in our hearts. Self-knowledge is the key to the precepts and doctrines of Scripture. The very utmost any outward notices of religion can do, is to startle us and make us turn inward and search our hearts; and then, when we have experienced what it is to read ourselves, we shall profit by the doctrines of the Church and the Bible.
Of course self-knowledge admits of degrees. No one perhaps, is entirely ignorant of himself; and even the most advanced Christian knows himself only "in part." However, most men are contented with a slight acquaintance with their hearts, and therefore a superficial faith. This is the point which it is my purpose to insist upon. Men are satisfied to have numberless secret faults. They do not think about them, either as sins or as obstacles to strength of faith, and live on as if they had nothing to learn.