When we thus learn by ourselves instead of learning from others, our ideas are far more definite and clear. Besides, if our reason is not accustomed to slavish submission to authority, this discovering relations, linking one idea to another, and inventing apparatus, renders us much more ingenious. If, instead, we take everything just as it is given to us, we allow our minds to sink down into indifference; just as a man who always lets his servants dress him and wait on him, and his horses carry him about, loses finally not only the vigor but even the use of his limbs. Boileau boasted that he had taught Racine to rhyme with difficulty. There are many excellent labor-saving methods for studying science; but we are in sore need of one to teach us how to learn them with more effort of our own.
The most manifest value of these slow and laborious researches is, that amid speculative studies they maintain the activity and suppleness of the body, by training the hands to labor, and creating habits useful to any man. So many instruments are invented to aid in our experiments and to supplement the action of our senses, that we neglect to use the senses themselves. If the graphometer measures the size of an angle for us, we need not estimate it ourselves. The eye which measured distances with precision intrusts this work to the chain; the steelyard saves me the trouble of measuring weights by the hand. The more ingenious our apparatus, the more clumsy and awkward do our organs become. If we surround ourselves with instruments, we shall no longer find them within ourselves.
But when, in making the apparatus, we employ the skill and sagacity required in doing without them, we do not lose, but gain. By adding art to nature, we become more ingenious and no less skilful. If, instead of keeping a child at his books, I keep him busy in a workshop, his hands labor to his mind's advantage: while he regards himself only as a workman he is growing into a philosopher. This kind of exercise has other uses, of which I will speak hereafter; and we shall see how philosophic amusements prepare us for the true functions of manhood.
I have already remarked that purely speculative studies are rarely adapted to children, even when approaching the period of youth; but without making them enter very deeply into systematic physics, let all the experiments be connected by some kind of dependence by which the child can arrange them in his mind and recall them at need. For we cannot without something of this sort retain isolated facts or even reasonings long in memory.