A true movement of carriages is dependent upon the amount or wearing power of their bearing surface, how this surface is disposed in reference to the strain to be resisted, and the conditions under which the sliding surfaces move; that is, how kept in contact. The cutting strain which is to be mainly considered, falls usually at an angle of thirty to forty degrees downward toward the front, from the centre of the lathe. To resist such strain a flat top shear presents no surface at right angles to the strain; the bearings are all oblique, and not only this, but all horizontal strain falls on one side of the shear only; for this reason, flat top shears have to be made much heavier than would be required if the sum of their cross section could be employed to resist transverse strain. This difficulty can, however, be mainly obviated by numerous cross girts, which will be found in most lathe frames having flat tops.The Stoic arguments are, indeed, when we come to analyse them, appeal to authority rather than to the logical understanding. We are told again and again that the common objects of desire and dread cannot really be good or evil, because they are not altogether under our control.55 And if we ask why this necessarily excludes them from the class of things to be pursued or avoided, the answer is that man, having been created for perfect happiness, must also have been created with the power to secure it by his own unaided exertions. But, even granting the very doubtful thesis that there is any ascertainable purpose in creation at all, it is hard to see how the Stoics could have answered any one who chose to maintain that man is created for enjoyment; since, judging by experience, he has secured a larger share of it than of virtue, and is just as capable of gaining it by a mere exercise of volition. For the professors of the Porch fully admitted that their ideal sage had never been realised; which, with their opinions about the indivisibility of virtue, was equivalent to saying that there never had been such a thing as a good25 man at all. Or, putting the same paradox into other words, since the two classes of wise and foolish divide humanity between them, and since the former class has only an ideal existence, they were obliged to admit that mankind are not merely most of them fools, but all fools. And this, as Plutarch has pointed out in his very clever attack on Stoicism, is equivalent to saying that the scheme of creation is a complete failure.56
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This analogy with subsequent developments is aided, so far as it goes, by the admixture of a certain Platonic element with Virgils Stoicism, shown chiefly by the references to an antenatal existence of the soul, introduced for the purpose of bringing Romes future heroes on the scene. This, however, is the last example of an attempt on the part of a Roman writer to combine Platos teaching with Stoicism.286 At a time when the Romans were more conscious of their literary dependence on Greece than was the case after the Augustan age had reached its zenith, they were probably drawn by the beauty of its literary form to study a system which could otherwise interest them but little. Thus, not only is Cicero full of admiration for Platoas, indeed, might be expected with so highly cultivated a disciple of the Academybut Cato, according to the well-known story, spent his last hours reading and re-reading the Phaedo; and his nephew Brutus also occupied an intermediate position between the Old Academy and the Porch. The Roman love of simplification and archaism induced subsequent thinkers either to let Platonism drop altogether, or to study those elements in which it differed from the pure naturalistic doctrine under their Pythagorean form. It may even be doubted whether Virgils psychology is not derived from Pythagoras rather than from Plato; Ovid, so far as he philosophises at all, is unquestionably a follower of the former;287 and in the moral teaching of the Sextii, who flourished under Augustus, Pythagorean principles are blended with Stoicism.288 It is another manifestation of the same effort to grasp every Greek doctrine by its roots, that Horace should proclaim himself the disciple of Aristippus rather than of Epicurus.289 Even he, however, feels183 himself drawn with advancing years towards the nobler faith which was now carrying all before it.290241We may, indeed, fairly ask what guarantee against wrong-doing of any kind could be supplied by a system which made the supreme good of each individual consist in his immunity from pain and fear, except that very pain or fear which he was above all things to avoid? The wise man might reasonably give his assent to enactments intended for the common good of all men, including himself among the number; but when his concrete interest as a private citizen came into collision with his abstract interests as a social unit, one does not see how the quarrel was to be decided on Epicurean principles, except by striking a balance between the pains respectively resulting from justice and injustice. Here, Epicurus, in his anxiety to show that hedonism, rightly understood, led to the same results as the accepted systems of morality, over-estimated the policy of honesty. There are cases in which the wrong-doer may count on immunity from danger with more confidence than when entering on such ordinary enterprises as a sea-voyage or a commercial speculation; there are even cases where a single crime might free him from what else would be a lifelong dread. And, at worst, he can fall back on the Epicurean arguments proving that neither physical pain nor death is to be feared, while the threats of divine vengeance are a baseless dream.147