ONE:For compasses, the lead points should be cylindrical, and fit into a metal sheath without paper packing or other contrivance to hold them; and if a draughtsman has instruments not arranged in this manner, he should have them changed at once, both for convenience and economy.It will be remembered that in an earlier section of this chapter we accompanied Plato to a period when he had provisionally adopted a theory in which the Protagorean contention that virtue can be taught was confirmed and explained by the Socratic contention that virtue is knowledge; while this knowledge again was interpreted in the sense of a hedonistic calculus, a prevision and comparison of the pleasures and pains consequent on our actions. We have now to trace the lines of thought by which he was guided to a different conception of ethical science.
TWO:So far, Aristotle regards the soul as a function, or energy, or perfection of the body, from which it can no more be separated than vision from the eye. It is otherwise with the part of mind which he calls Nous, or Reasonthe faculty which takes cognisance of abstract ideas or the pure forms of things. This corresponds, in the microcosm, to the eternal Nous of the macrocosm, and, like it, is absolutely immaterial, not depending for its activity on the exercise of any bodily organ. There is, however, a general analogy between sensation and thought considered as processes of cognition. Previous to experience, the Nous is no thought in particular, but merely a possibility of thinking, like a smooth wax tablet waiting to be written on. It is determined to some particular idea by contact with the objective forms of things, and in this determination is raised from power to actuality. The law of moderation, however, does not apply to thought. Excessive stimulation is first injurious and then destructive to the organs of sense, but we cannot have too much of an idea; the more intense it is the better are we able to conceive all the367 ideas that come under it, just because ideation is an incorporeal process. And there seems to be this further distinction between sensation and thought, that the latter is much more completely identified with its object than the former; it is in the very act of imprinting themselves on the Nous that the forms of things become perfectly detached from matter, and so attain their final realisation. It is only in our consciousness that the eternal ideas of transient phenomena become conscious of themselves. Such, we take it, is the true interpretation of Aristotles famous distinction between an active and a passive Nous. The one, he tells us, makes whatever the other is made. The active Nous is like light raising colours from possibility to actuality. It is eternal, but we have no remembrance of its past existence, because the passive Nous, without which it can think nothing, is perishable.Any truth in mechanics, even the action of the "mechanical powers" before alluded to, is received with an air of mystery, unless the nature of power is first understood. Practical demonstration a hundred times repeated does not create a conviction of truth in mechanical propositions, unless the principles of operation are understood.
