“In John’s well-known and well-loved work, On the Priesthood, he compares the Christian pastor to a physician, one who has ‘discovered a multiplicity of drugs and various designs of instruments and appropriate forms of diet for the sick.’ John notes, however, that occasionally a healthy climate or deep sleep makes intervention by a physician unnecessary. Not so with physicians of the word. The preacher must carefully diagnose the ills and needs of his congregation, faithfully applying the only efficacious remedy, ‘teaching by word of mouth.’
That is the best instrument, the best diet, and the best climate. It takes the place of medicine and cautery and surgery. When we need to cauterize or cut, we must use this. Without it all else is useless. By it we rouse the soul’s lethargy or reduce its inflammation, we remove excrescences and supply defects, and, in short, do everything which contributes to its health. … We must take great care, therefore, that against a single kind of attack. … Unless the man who means to win understands every aspect of the art, the devil knows how to introduce his agents at a single neglected spot and so to plunder the flock. But he is baffled when he sees that the shepherd has mastered his whole repertoire and thoroughly understands his tricks” (p. 95).