Experimental Physics.
The earth has different climates, and these have different temperatures. As we approach the poles the variation of seasons is more perceptible,—all bodies contract with cold and expand with heat. This effect is more readily measured in liquids, and is particularly noticeable in spirituous liquors. This fact suggested the idea of the thermometer. The wind strikes our faces; air is therefore a body, a fluid; we feel it though we cannot see it. Turn a glass vessel upside down in water, and the water will not fill it unless you leave a vent for the air; therefore air is capable of resistance. Sink the glass lower, and the water rises in the air-filled region of the glass, although it does not entirely fill that space. Air is therefore to some extent compressible. A ball filled with compressed air bounds much better than when filled with anything else: air is therefore elastic. When lying at full length in the bath, raise the arm horizontally out of the water, and you feel it burdened by a great weight; air is therefore heavy. Put air in equilibrium with other bodies, and you can measure its weight. From these observations were constructed the barometer, the siphon, the air-gun, and the air-pump. All the laws of statics and hydrostatics were discovered by experiments as simple as these. I would not have my pupil study them in a laboratory of experimental physics. I dislike all that array of machines and instruments. The parade of science is fatal to science itself. All those machines frighten the child; or else their singular forms divide and distract the attention he ought to give to their effects.
I would make all our own machines, and not begin by making the instrument before the experiment has been tried. But after apparently lighting by chance on the experiment, I should by degrees invent instruments for verifying it. These instruments should not be so perfect and exact as our ideas of what they should be and of the operations resulting from them.
For the first lesson in statics, instead of using balances, I put a stick across the back of a chair, and when evenly balanced, measure its two portions. I add weights to each part, sometimes equal, sometimes unequal. Pushing it to or fro as may be necessary, I finally discover that equilibrium results from a reciprocal proportion between the amount of weight and the length of the levers. Thus my little student of physics can rectify balances without having ever seen them.
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.
In investigating the laws of nature, always begin with the most common and most easily observed phenomena, and accustom your pupil not to consider these phenomena as reasons, but as facts. Taking a stone, I pretend to lay it upon the air; opening my hand, the stone falls. Looking at Émile, who is watching my motions, I say to him, "Why did the stone fall?"
No child will hesitate in answering such a question, not even Émile, unless I have taken great care that he shall not know how. Any child will say that the stone falls because it is heavy. "And what does heavy mean?" "Whatever falls is heavy." Here my little philosopher is really at a stand. Whether this first lesson in experimental physics aids him in understanding that subject or not, it will always be a practical lesson.
Nothing to be Taken upon Authority.
Learning from the Pupil's own Necessities.
As the child's understanding matures, other important considerations demand that we choose his occupations with more care. As soon as he understands himself and all that relates to him well enough and broadly enough to discern what is to his advantage and what is becoming in him, he can appreciate the difference between work and play, and to regard the one solely as relaxation from the other. Objects really useful may then be included among his studies, and he will pay more attention to them than if amusement alone were concerned. The ever-present law of necessity early teaches us to do what we dislike, to escape evils we should dislike even more. Such is the use of foresight from which, judicious or injudicious, springs all the wisdom or all the unhappiness of mankind.
We all long for happiness, but to acquire it we ought first to know what it is. To the natural man it is as simple as his mode of life; it means health, liberty, and the necessaries of life, and freedom from suffering. The happiness of man as a moral being is another thing, foreign to the present question. I cannot too often repeat that only objects purely physical can interest children, especially those who have not had their vanity aroused and their nature corrupted by the poison of opinion.
When they provide beforehand for their own wants, their understanding is somewhat developed, and they are beginning to learn the value of time. We ought then by all means to accustom and to direct them to its employment to useful ends, these being such as are useful at their age and readily understood by them. The subject of moral order and the usages of society should not yet be presented, because children are not in a condition to understand such things. To force their attention upon things which, as we vaguely tell them, will be for their good, when they do not know what this good means, is foolish. It is no less foolish to assure them that such things will benefit them when grown; for they take no interest in this supposed benefit, which they cannot understand.
Let the child take nothing for granted because some one says it is so. Nothing is good to him but what he feels to be good. You think it far sighted to push him beyond his understanding of things, but you are mistaken. For the sake of arming him with weapons he does not know how to use, you take from him one universal among men, common sense: you teach him to allow himself always to be led, never to be more than a machine in the hands of others. If you will have him docile while he is young, you will make him a credulous dupe when he is a man. You are continually saying to him, "All I require of you is for your own good, but you cannot understand it yet. What does it matter to me whether you do what I require or not? You are doing it entirely for your own sake." With such fine speeches you are paving the way for some kind of trickster or fool,—some visionary babbler or charlatan,—who will entrap him or persuade him to adopt his own folly.
A man may be well acquainted with things whose utility a child cannot comprehend; but is it right, or even possible, for a child to learn what a man ought to know? Try to teach the child all that is useful to him now, and you will keep him busy all the time. Why would you injure the studies suitable to him at his age by giving him those of an age he may never attain? "But," you say, "will there be time for learning what he ought to know when the time to use it has already come?" I do not know; but I am sure that he cannot learn it sooner. For experience and feeling are our real teachers, and we never understand thoroughly what is best for us except from the circumstances of our case. A child knows that he will one day be a man. All the ideas of manhood that he can understand give us opportunities of teaching him; but of those he cannot understand he should remain in absolute ignorance. This entire book is only a continued demonstration of this principle of education.