menced (for if the whole be read hurriedly, some useful point may easily escape the mind); (9) finally, when the whole has been carefully perused, the reader may proceed to distinguish between those points that are necessary and those that are superfluous.
15. These points should be observed by those who teach the sciences, and may be expressed in nine very useful precepts.
(i) Whatever is to be known must be taught.
Unless that which is to be known be placed before a pupil, how is he to acquire a knowledge of it? Therefore let those who teach beware of concealing anything from their pupils, whether of intent, do the envious and dishonest, or through carelessness, as is the case with those who perform their duties in a perfunctory manner. The two things necessary are honesty and hard work.
16. (ii) Whatever is taught should be taught as being of practical application in every-day life and of some definite use.
That is to say, the pupil should understand that what he learns is not taken out of some Utopia or borrowed from Platonic Ideas, but is one of the facts which surround us, and that a fitting acquaintance with it will be of great service in life. In this way his energy and his accuracy will be increased.
17. (iii) Whatever is taught should be taught straightforwardly, and not in a complicated manner.
This means that we must look straight at objects and not squint, for in that case the eyes do not see that at which they look, but rather distort and confuse it. Objects should be placed before the eyes of the student in their true character, and not shrouded in words, metaphors, or hyperboles. These devices have their use if the object be to exaggerate or to detract from, to praise or to blame what is already known. But when knowledge is being acquired they should be avoided and the facts should be set forth plainly.
18. (iv) Whatever is taught must be taught with reference
