THREE:Again, Hobbes differs wholly from Bacon in the deductive character of his method. His logic is the old syllogistic system reorganised on the model of mathematical analysis. Like all the great thinkers of his time, he was a geometrician and a mechanical physicist, reasoning from general to particular propositions and descending from causes to effects.554397 His famous theory of a social contract is a rational construction, not a historical narrative. But though a mathematician, he shows no traces of Platonic influence. He is, therefore, all the more governed by Atomist and Stoic modes of thought. He treats human nature, single and associated, as Galileo and Descartes had treated motion and space. Like them, too, he finds himself in constant antagonism to Aristotle. The description of man as a social animal is disdainfully rejected, and the political union resolved into an equilibrium of many opposing wills maintained by violent pressure from without. In ethics, no less than in physics, we find attractive forces replaced by mechanical impacts.
THREE:It is, at any rate, certain that the successors of Aenesidmus adhered to the standpoint of Pyrrho. One of them, Agrippa, both simplified and strengthened the arguments of the school by reducing the ten Tropes to five. The earlier objections to human certainty were summed up under two heads: the irreconcilable conflict of opinions on all subjects; and the essential relativity of consciousness, in which the percipient and the perceived are so intimately united that what things in themselves are cannot possibly be discovered. The other three Tropes relate to the baselessness of reasoning. They were evidently suggested by Aristotles remarks on the subject. The process of proof cannot be carried backwards ad infinitum, nor can it legitimately revolve in a circle. Thus much had already been admitted, or rather insisted on by the great founder of logic. But the Sceptics could not agree to Aristotles contention, that demonstration may be based on first principles of self-evident certainty. They here fell back on their main argument; that the absence of general agreement on every point is fatal to the existence of such pretended axioms. A still further simplification was effected by the reduction of the five Tropes to twothat all reasoning rests on intuition, and that mens intuitions are irreconcilably at variance with one another.300 As against true science, the sceptical Tropes are powerless, for the validity of its principles has nothing to do189 with their general acceptance. They are laid before the learner for his instruction, and if he chooses to regard them as either false or doubtful, the misfortune will be his and not theirs. But as against all attempts to constrain belief by an appeal to authority, the Tropes still remain invincible. Whether the testimony invoked be that of ancient traditions or of a supposed inward witness, there is always the same fatal objection that other traditions and other inward witnesses tell quite a different story. The task of deciding between them must, after all, be handed over to an impersonal reason. In other words, each individual must judge for himself and at his own risk, just as he does in questions of physical science.
THREE:It seems strange that Galileo, having gone so far, did not go a step further, and perceive that the planetary orbits, being curvilinear, must result from the combination of a centripetal with a tangential force. But the truth is that he never seems to have grasped his own law of inertia in its full generality. He understood that the planets could not have been set in motion without a rectilinear impulse; but his idea was that this impulse continued only so long as was necessary in order to give them their present velocity, instead of acting on them for ever as a tangential force. The explanation of this strange inconsequence must be sought in a survival of Aristotelian conceptions, in the persistent belief that rectilinear motion was necessarily limited and temporary, while circular motion was natural, perfect, and eternal.548 Now such conceptions as386 Nature, perfection, and eternity always rebel against an analysis of the phenomena wherein they are supposed to reside. The same prejudice will explain why Galileo should have so persistently ignored Keplers Laws, for we can hardly imagine that they were not brought under his notice.
TWO:As remarked in the case of other machines treated of, there is no use of describing the mechanism of trip-hammers; it is presumed that every engineer apprentice has seen trip-hammers, or can do so; and the plan here is to deal especially with what he cannot see, and would not be likely to learn by casual observation.Bruce put the whole thing resolutely out of his mind, and went to bed. It was not till after luncheon that he found time to see Lawrence, to whom he told Hetty's story and the strange scene he had witnessed the night before.
TWO: