Book 4
7.2
He also taught them how far a well-educated man should make himself familiar with any given subject.For instance, he said that the study of geometry should be pursued until the student was competent to measure a parcel of land accurately in case he wanted to take over, convey or divide it, or to compute the yield; and this knowledge was so easy to acquire, that anyone who gave his mind to mensuration knew the size of the piece and carried away a knowledge of the principles of land measurement.
7.3
He was against carrying the study of geometry so far as to include the more complicated figures, on the ground that he could not see the use of them. Not that he was himself unfamiliar with them, but he said that they were enough to occupy a lifetime, to the complete exclusion of many other useful studies.
7.4
Similarly he recommended them to make themselves familiar with astronomy, but only so far as to be able to find the time of night, month and year, in order to use reliable evidence when planning a journey by land or sea, or setting the watch, and in all other affairs that are done in the night or month or year, by distinguishing the times and seasons aforesaid. This knowledge, again, was easily to be had from night hunters and pilots and others who made it their business to know such things.
7.5
But he strongly deprecated studying astronomy so far as to include the knowledge of bodies revolving in different courses, and of planets and comets, and wearing oneself out with the calculation of their distance from the earth, their periods of revolution and the causes of these. Of such researches, again he said that he could not see what useful purpose they served. He had indeed attended lectures on these subjects too; but these again, he said, were enough to occupy a lifetime to the complete exclusion of many useful studies.
