in the ranks and in command, on foot and on horseback, in sea-fight and in siege. In common warfare, indeed, each man repels the enemy by discharging the particular duty which he has undertaken. But here it is otherwise; and if any one wishes to come off conqueror in this warfare, he must understand all forms of the art, as the devil knows well how to introduce his own assailants through any one spot which may happen to be unguarded, and to carry off the sheep. But not so where he perceives the shepherd coming equipped with accurate knowledge at all points, and well acquainted with his plottings. Wherefore we ought to be well-guarded in all parts: for a city, so long as it happens to be surrounded with a wall, laughs to scorn the besiegers, abiding in great security; but if any one makes a breach in the wall, though but of the size of a gate, the rest of the circuit is of no use, although the whole of it stand quite securely; so it is with the city of God: so long as the presence of mind and wisdom of the shepherd, which answers to the wall, protect it on all sides, all the enemy’s devices end in his confusion and ridicule, and they who dwell within the wall abide unmolested, but wherever any one has been able to demolish a single part, though the rest stand never so fast, through that breach ruin will enter upon the whole. For to what purpose does a man contend earnestly with the Greeks, if at the same time he becomes a prey to the Jews? or get the better of both these and then fall into the clutches of the Manichæans?153 or after he has proved himself superior to them even, if they who introduce fatalism154 enter in, and make havoc of the flock? But not to enumerate all the heresies of the devil, it will be enough to say that unless the shepherd is well skilled in refuting them all, the wolf, by means of any one of them, can enter, and devour the greater part of the flock. In ordinary warfare we must always look for victory being won or defeat sustained by the soldiers who are on the field of battle. But in the spiritual warfare the case is quite different. For there it often happens that the combat with one set of enemies secures a victory for others who never engaged in battle at all, nor took any trouble, but were sitting still all the while; and he who has not much experience in such occurrences will get pierced, so to say, with his own sword, and become the laughing-stock of friends and foes alike. I will try by an example to make clear what I am saying. They who receive the wild doctrines of Valentinus and Marcion,155 and 153 The followers of Manes, or Manichæus, who was born about 240 A.D. He taught that God was the cause of good, and matter the cause of evil. This theory about matter led him to hold that the body of Jesus was an incorporeal phantom. He eliminated the Old Testament from the Scriptures, and held himself at liberty also to reject such passages in the New Testament as were opposed to his own opinions. See Robertson: Hist. of the Christian Church, vol. i. 139–145. 154 “οἱ την ›ιμαρμν™ην ἐισ€γοντες,” sc. The Stoics. They were still a numerous body, and St. Chrysostom himself wrote six Homilies against them. 155 Marcion and Valentinus (A.D. 140) were each founders of a form of Gnosticism. Each held that the God of the Old Testament was morally contrary to the God of the New: while the system of Valentinus represented the imaginative and speculative side of Gnosticism, that of Marcion represented its practical side, and was rather 93 Book IV