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We have seen how Carneades, alike in his theory of probability and in his ethical eclecticism, had departed from the extreme sceptical standpoint. His successor, Clitomachus, was content with committing the doctrines of the master to writing. A further step was taken by the next Scholarch, Philo, who is known as the Larissaean, in order to distinguish him from his more celebrated namesake, the Alexandrian Jew. This philosopher asserted that the negations of the New Academy were not to be taken as a profession of absolute scepticism, but merely as a criticism on the untenable pretensions of the Stoa. His own position was that, as a matter of fact, we have some certain knowledge of the external world, but that no logical account can be given of the process by which it is obtained��we can only say that such an assurance has been naturally stamped on our minds.254 This is the theory of intuitions or innate ideas, still held by many persons; and, as such, it marks a return to pure Platonism, having been evidently suggested by the semi-mythological fancies of the161 Meno and the Phaedrus. With Philo as with those Scotch professors who long afterwards took up substantially the same position, the leading motive was a practical one, the necessity of placing morality on some stronger ground than that of mere probability. Neither he nor his imitators saw that if ethical principles are self-evident, they need no objective support; if they are derivative and contingent, they cannot impart to metaphysics a certainty which they do not independently possess. The return to the old Academic standpoint was completed by a much more vigorous thinker than Philo, his pupil, opponent, and eventual successor, Antiochus. So far from attempting any compromise with the Sceptics, this philosopher openly declared that they had led the school away from its true traditions; and claimed for his own teaching the merit of reproducing the original doctrine of Plato.255 In reality, he was, as Zeller has shown, an eclectic.256 It is by arguments borrowed from Stoicism that he vindicates the certainty of human knowledge. Pushing the practical postulate to its logical conclusion, he maintains, not only that we are in possession of the truth, but also��what Philo had denied��that true beliefs bear on their face the evidence by which they are distinguished from illusions. Admitting that the senses are liable to error, he asserts the possibility of rectifying their mistakes, and of reasoning from a subjective impression to its objective cause. The Sceptical negation of truth he meets with the familiar argument that it is suicidal, for to be convinced that there can be no conviction is a contradiction in terms; while to argue that truth is indistinguishable from falsehood implies an illogical confidence in the validity of logical processes; besides involving the assumption that there are false appearances and that they are known to us as such, which would be impossible unless we were in a position to compare them with the corresponding162 truths.257 For his own part, Antiochus adopted without alteration the empirical theory of Chrysippus, according to which knowledge is elaborated by reflection out of the materials supplied by sense. His physics were also those of Stoicism with a slight Peripatetic admixture, but without any modification of their purely materialistic character. In ethics he remained truer to the Academic tradition, refusing to follow the Stoics in their absolute isolation of virtue from vice, and of happiness from external circumstances, involving as it did the equality of all transgressions and the worthlessness of worldly goods. But the disciples of the Porch had made such large concessions to common sense by their theories of preference and of progress, that even here there was very little left to distinguish his teaching from theirs.258

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"'The Tragedy of the Corner House.'"Milling relates to metal cutting with serrated rotary cutters, and differs in many respects from either planing or turning. The movement of the cutting edges can be more rapid than with tools which act continuously, because the edges are cooled during the intervals between each cut; that is, if a milling tool has twenty teeth, any single tooth or edge acts only from a fifteenth to a twentieth part of the time; and as the cutting distance or time of cutting is rarely long enough to generate much heat, the speed of such tools may be one-half greater than for turning, drilling, or planing tools. Another distinction between milling and other tools is the perfect and rigid manner in which the cutting edges are supported; they are short and blunt, besides being usually carried on short rigid mandrils. A result of this rigid support of the tools is seen in the length of the cutting edges that can be employed, which are sometimes four inches or more in length. It is true the amount of material cut away in milling is much less than the edge movement will indicate when compared with turning or planing; yet the displacing capacity of a milling machine exceeds that of either a lathe or a planing machine. Theoretically the cutting or displacing capacity of any metal or wood cutting machine, is as the length of the edges multiplied into the speed of their cutting movement; a rule which applies very uniformly in wood cutting, and also in metal cutting within certain limits; but the strains that arise in metal cutting are so great that they may exceed all means of resisting them either in the material acted upon, or in the means of supporting tools, so that the length of cutting edges is limited. In turning chilled rolls at Pittsburg, [141] tools to six inches wide are employed, and the effect produced is as the length of the edge; but the depth of the cut is slight, and the operation is only possible because of the extreme rigidity of the pieces turned, and the tools being supported without movable joints as in common lathes.

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