Pompey, when about to enter for the first time on the office of Consul, being ignorant of city manners and senatorial forms, requested Varro to frame for him a written commentary or manual, from which he might learn the duties to be discharged by him when he convened the Senate. This book, which was entitled _Isagogicum de Officio Senatus habendi_, Varro says, in the letters which he wrote to Oppianus, had been lost. But in these letters he repeated many things on the subject, as what he had written before had perished(76).
The _philosophical_ writings of Varro are not numerous; but his chief work of that description, entitled _De Philosophia Liber_, appears to have been very comprehensive. St Augustine informs us that Varro examined in it all the various sects of philosophers, of which he enumerated upwards of 280. The sect of the old Academy was that which he himself followed, and its tenets he maintained in opposition to all others. He classed these numerous sects in the following curious manner: All men chiefly desire, or place their happiness in, four things--pleasure--rest--these two united, (which Epicurus, however, termed pleasure,) or soundness of body and mind. Now, philosophers have contended that virtue is to be sought after for the sake of obtaining one or other of these four; or, that some one of these four is to be sought after for the sake of virtue; or, that they and virtue also are to be sought after for their own sake, and from these different opinions each of the four great objects of human desire being sought after with three different views, there are formed twelve sects of philosophers. These twelve sects are doubled, in consequence of the different opinions created by the considerations of social intercourse--some maintaining that the four great desires should be gratified for our own sake, and others, that they should be indulged only for the sake of our neighbours. The above twenty-four sects become forty-eight, from each system being defended as certain truth, or as merely the nearest approximation to probability--twenty-four sects maintaining each hypothesis as certain, and twenty-four as only probable. These again were doubled, from the difference of opinion with regard to the suitable garb and external habit and demeanour of philosophers.