[Scripture], by which, “as in a glass, we may survey ourselves, and know what manner of persons we are,” (James 1. 23) discovers ourselves to us; pierces into the inmost recesses of the mind; strips off every disguise; lays open the inward part; makes a strict scrutiny into the very soul and spirit; and critically judges of the thoughts and intents of the heart. (Heb. iv. 12) It shows us with what exactness and care we are to search and try our spirits, examine ourselves, and watch our ways, and keep our hearts, in order to acquire this important self-science; which it often calls us to do. “Examine yourselves; prove your own selves; know you not yourselves? Let a man examine himself.” (1 Cor. xi. 28)
John Mason, A Treatise on Self-Knowledge (1745)