Moreover he wishes us to have around us a breastplate and a buckler. For desire is a wild beast which easily springs forth, and we shall have need of walls and fences innumerable, to overcome, and to restrain it. And for this cause God has built this part [of our body] especially with bones, as with a kind of stones, placing around it a support, so that [desire] might not at any time, having broken or cut through, easily injure the whole man. For it is a fire (it is said) and a great tempest, and no other part of the body could endure this violence. And the sons of the physicians too say that for this cause the lungs have been spread under the heart, so that the heart being itself [put] into something soft and tender, by beating as it were into a sort of sponge, may continually be rested, and not [by striking] against the resisting and hard sternum, receive hurt through the violence of its beatings. We have need therefore of a strong breastplate, so as to keep this wild beast alway quiet.