the foundation be firm, a solid edifice can be constructed upon it, but if it be weak this is impossible. According to the observations of physicians, the initial defects of digestion cannot be repaired later on, and similarly in any operation an error at the beginning vitiates all that follows. For this reason Timotheus the musician used to demand twice as large a fee from those pupils who had learned the rudiments of their art elsewhere, saying that his labour was twofold, as he had first to get them out of the bad habits that they had acquired, and then to teach them correctly. Those, therefore, who are learning any art should take care to make themselves masters of the rudiments by imitating their copies accurately. This difficulty once overcome, the rest follows of itself, just as a city lies at the mercy of foes when its gates are broken in. All haste should be avoided, lest we proceed to advanced work before the elementary stages have been mastered. He goes fast enough who never quits the road, and a delay which is caused by obtaining a thorough grip of first principles is really no delay, but an advance towards mastering what follows with ease, speed, and accuracy.
13. (ix) Errors must be corrected by the master on the spot; but precepts, that is to say the rules, and the exceptions to the rules, must be given at the same time.
Hitherto we have urged that the arts be taught rather by example than by precept: we now add that precepts and rules must be given as well, that they may guide the operations and prevent error. That is to say, the less obvious points of the model should be clearly explained, and it should be made evident how the operation should begin, what it should aim at, and how that aim can be realised. Reasons should also be given for each rule. In this way a thorough knowledge of the art, and confidence and exactness in imitating, will be attained.
But these rules should be as short and as simple as possible, since we do not want to grow gray while acquiring them. When once mastered they should be of perpetual use, even when laid aside, just as knee-bands are of
