arranged cover the whole subject and contain a great deal of matter in a short space (Ecclesiasticus xxxii. 8)—that is to say, which place before the scholar the whole of the subject-matter by means of a small number of rules and definitions expressed in the simplest and clearest language, and sufficient in themselves to lead to more profound study.
Sixth Problem
How is it possible to do two or three things by a single operation?
41. The example of nature shows that several things can be done at one time and by means of the same operation. It is an undoubted fact that a tree grows above the ground and beneath it at the same time, and that its wood, its bark, its leaves, and its fruit, all develope simultaneously. The same observation applies to animals, whose limbs all develope and grow stronger at the same time. Further, each limb performs several operations. The feet, for instance, not only support a man but also move him forwards and backwards in various ways. The mouth is not only the entrance to the body, but also serves as a masticator and as a trumpet that sounds whenever called upon to do so. With a single inspiration the lungs cool the heart, purify the brain, and assist in voice-production.
42. We find the same thing in the arts: (1) In the sun-dial, the single shadow cast by the gnomon points out the hour of the day, the sign of the zodiac in which the sun is moving, the length of the day and of the night, the day of the month, and several other things. (2) One pole serves to direct, to turn, and to hold back a carriage. (3) A good orator or writer instructs, excites, and pleases at the same time, even though his subject may make it difficult to combine these three elements.
43. The instruction of the young should be similarly organised, so that every activity may produce several results. It may be laid down as a general rule that each
