He takes his examples from Roman history, and particularly considers the case of Regulus in the obligation of his oath, and the advice which he gave to the Roman Senate. The author disclaims having been indebted to any preceding writers on this subject; but it appears, from what he afterwards states, that the sixth book of the work of Hecato, a scholar of Panætius, was full of questions of this kind: As, for example—If something must be thrown into the sea to lighten a vessel in a storm, whether one should sacrifice a valuable horse, or a worthless slave? Whether, if, during a shipwreck, a fool has got hold of a plank, a wise man ought to take it from him, if he be able? If one, unknowingly, receives bad money for his goods, may he pay it away to a third hand, after he is aware that it is bad? Diogenes, it seems, one of the three philosophic ambassadors who came to Rome from Athens, in the end of the sixth century, maintained the affirmative of this last proposition. The subject being too extensive for dialogue, (the form of his other philosophical treatises,) the author has addressed the work _De Officiis_ to his son, and has represented it as written for his instruction. “It is,” says Kelsall, “the noblest present ever made by a parent to a child.” Cicero declares, that he intended to treat in it of all the duties(454); but it is generally considered to have been chiefly drawn up as a manual of political morality, and as a guide to young Romans of his son’s age and distinction, which might enable them to attain political eminence, and to tread with innocence and safety “the slippery steeps of power.” _De Senectute_.—— “O Thou all eloquent, whose mighty mind Streams from the depths of ages on mankind, Streams like the day—who angel-like hast shed Thy full effulgence on the hoary head; Speaking in Cato’s venerable voice— “Look up and faint not—faint not, but rejoice”— From thy Elysium guide us(455).”