ONE:The Academic theory of probability bears some resemblance to the Canonic of Epicurus, and may have been partially suggested by it. Both are distinguished from the Aristotelian and Stoic logic by the care with which they provide for the absence of contradictory evidence. In this point, however, the superiority of Carneades to Epicurus is very marked. It is not enough for him that a present impression should suggest a belief not inconsistent with past experience; in the true inductive spirit, he expressly searches for negative instances, and recommends the employment of experiment for this purpose. Still more philosophical is the careful and repeated analysis of attendant circumstances, a precaution not paralleled by anything in the slovenly method of his predecessor. Here the great value of scepticism as an element in mental training becomes at once apparent. The extreme fallibility of the intellectus sibi permissus had to be established before precautions could be adopted for its restraint. But the evidence accepted in proof of this fallibility has been very different at different times, and has itself given rise to more than one fallacious interpretation. With us it is, for the most part, furnished by experience. The circumstance that many demonstrable errors were formerly received as truths is quite sufficient to put us on our guard against untested opinions. With Bacon, it was not the erroneousness of previous systems, but their barrenness and immobility, which led him to question the soundness of their logic; and his doubts were confirmed by an analysis of the disturbing influences under which mens judgments are formed. The ancient Sceptics were governed entirely by priori considerations. Finding themselves confronted by an immense mass of contradictory opinions, they argued that some of these must be false as all could not possibly be true. And an analysis of the human faculties156 led them, equally on priori grounds, to the conclusion that these irreconcilable divergences were but the result and the reproduction of an interminable conflict carried on within the mind itself. They could not foresee how much time would do towards reducing the disagreement of educated opinion within a narrower compass. They did not know what the experience of experience itself would teach. And their criticisms on the logic and metaphysics of their opponents were rendered inconclusive, as against all certainty, by the extent to which they shared that logic and metaphysics themselves. Carneades, at least, seems to assume throughout that all existence is material, that there is a sharp distinction between subject and object in knowledge, and that there is an equally sharp distinction between sensation and reasoning in the processes by which knowledge is obtained. In like manner, his ethical scepticism all turns on the axiom, also shared by him with the Stoics, that for a man to be actuated by any motive but his own interest is mere folly.
ONE:An apprentice must guard against the too common impression that the engine, cylinder, piston, valves, and so on, are the main parts of steam machinery, and that the boiler and furnace are only auxiliaries. The boiler is, in fact, the base of the whole, that part where the power is generated, the engine being merely an agent for transmitting power from the boiler to work that is performed. This proposition would, of course, be reached by any one in reasoning about the matter and following it to a conclusion, but the fact should be fixed in the mind at the beginning.
ONE:The EndWe have also to note that Plotinus arrives at his Absolute by a method apparently very different from that pursued by either of his teachers. Platos primal beauty is, on the face of it, an abstraction and generalisation from all the scattered and imperfect manifestations of beauty to be met with in our objective experience. And Aristotle is led to his conception of an eternal immaterial thought by two lines of analysis, both starting from the phenomena of external Nature. The problem of his Physics is to account for the perpetuity of motion. The problem of his Metaphysics is to explain the transformation of potential into actual existence. Plotinus, on the other hand, is always bidding us look within. What we admire in the objective world is but a reflex of ourselves. Mind is the sole reality; and to grasp this reality under its highest form, we must become like it. Thus the more we isolate our own personality and self-identity from the other interests and experiences of life, the more nearly do we approach to consciousness of and coalescence with the supreme identity wherein all things have their source.
