Undoubtedly the notions of things thus acquired for oneself are clearer and much more convincing than those acquired from the teaching of others; and not only is our reason not accustomed to a slavish submission to authority, but we develop greater ingenuity in discovering relations, connecting ideas and inventing apparatus, than when we merely accept what is given us and allow our minds to be enfeebled by indifference, like the body of a man whose servants always wait on him, dress him and put on his shoes, whose horse carries him, till he loses the use of his limbs. Boileau used to boast that he had taught Racine the art of rhyming with difficulty. Among the many short cuts to science, we badly need some one to teach us the art of learning with difficulty. The most obvious advantage of these slow and laborious inquiries is this: the scholar, while engaged in speculative studies, is actively using his body, gaining suppleness of limb, and training his hands to labour so that he will be able to make them useful when he is a man. Too much apparatus, designed to guide us in our experiments and to supplement the exactness of our senses, makes us neglect to use those senses. The theodolite makes it unnecessary to estimate the size of angles; the eye which used to judge distances with much precision, trusts to the chain for its measurements; the steel yard dispenses with the need of judging weight by the hand as I used to do. The more ingenious our apparatus, the coarser and more unskilful are our senses. We surround ourselves with tools and fail to use those with which nature has provided every one of us. But when we devote to the making of these instruments the skill which did instead of them, when for their construction we use the intelligence which enabled us to dispense with them, this is gain not loss, we add art to nature, we gain ingenuity without loss of skill. If instead of making a child stick to his books I employ him in a workshop, his hands work for the development of his mind. While he fancies himself a workman he is becoming a philosopher. Moreover, this exercise has other advantages of which I shall speak later; and you will see how, through philosophy in sport, one may rise to the real duties of man. I have said already that purely theoretical science is hardly suitable for children, even for children approaching adolescence; but without going far into theoretical physics, take care that all their experiments are connected together by some chain of reasoning, so that they may follow an orderly sequence in the mind, and may be recalled at need; for it is very difficult to remember isolated facts or arguments, when there is no cue for their recall.