The earth when it has once received the seed, straightway gives forth its fruits, and needs not a second sowing; but with our souls it is not so, and one must be content, after having sown many times, and manifested much carefulness, to be able once to receive fruit. For in the first place, what is said settles in the mind with difficulty, because the ground is very hard, and entangled with thorns innumerable, and there are many which lay plots, and carry away the seed; afterwards, when it has been fixed and has taken root, it still needs the same attention, that it may come to maturity, and having done so may remain uninjured, and take no harm from any. For in the case of seeds, when the ear is fully formed and has gained its proper strength, it easily despises rust, and drought, and every other thing; but it is not so with doctrines; in their case after all the work has been fully done, one storm and flood often comes on, and either by the attack of unpleasant circumstances, or by the plots of men skilled to deceive, or by various other temptations brought against them, brings them to ruin.