2 I need not now conduct the stream of my discourse through the meadows of virtue, nor exert myself to show to you the beauty of its several flowers. I need not dilate on the purity of the lily, the modest blush of the rose, the royal purple of the violet, or the promise of glowing gems which their various colours hold out. For through the mercy of God you have already put your hand to the plough; you have already gone up upon the housetop like the apostle Peter. Who when he became hungry among the Jews had his hunger satisfied by the faith of Cornelius, and stilled the craving caused by their unbelief through the conversion of the centurion and other Gentiles. By the vessel let down from heaven to earth, the four corners of which typified the four gospels, he was taught that all men can be saved. Once more, this fair white sheet which in his vision was taken up again was a symbol of the church which carries believers from earth to heaven, an assurance that the Lord's promise should be fulfilled: “blessed are the pure in heart, for they shall see God.”
All this means that I take you by the hand and do my best to impress certain facts upon your mind; that, like a skilled sailor who has been through many shipwrecks, I am anxious to caution an inexperienced passenger of the risks before him. For on one side is the Charybdis of covetousness, “the root of all evil;” and on the other lurks the Scylla of detraction girt with the railing hounds of which the apostle says: “if you bite and devour one another, take heed that you be not consumed one of another.” Sometimes, you must know, the quicksands of vice suck us down as we sail at ease through the calm water; and the desert of this world is not untenanted by venomous reptiles.
Source: Letters (New Advent)