Having constantly in mind the practical errors under which these churches were suffering, he comes back again and again to the warning against that delusive tendency to exalt the outward. He exhorts them, not to imagine that it is sufficient to have a mere knowledge of the word, to be intellectually conversant with it. He warns them against the self-deception, that by such a knowledge merely they had complied with what he has just said, had really received the word into their life, had thus become Christians. The essential point is, the practical application of the word to the life. Herein must it manifest its efficacy, as a principle which works from within upon the outward character, and takes possession of the entire life. He says to them: "But be ye doers of the word and not hearers only, deceiving your own selves." He sets this in a clear light by a familiar illustration. He compares him who receives the word with the understanding only, without applying it to the life, to one who, having seen his image in a mirror, goes away and immediately forgets how he looked. Thus he who merely busies himself in a superficial way with the divine word, may have learned indeed what is the true aspect of his life in relation to the divine Law and its demands. A light has dawned upon his mind, as to what he is and should be. But turning away again from the divine word, hurried along by the current of life and by his own passions, he immediately forgets it all like him who just saw his image in the mirror, and all is of no avail. "For if any one be a hearer of the word and not a doer, he is like unto a man beholding his natural face in a glass; for he beholdeth himself, and goeth his way, and straightway forgetteth what manner of man he was."