In your inquiry into the laws of nature always begin with the commonest and most conspicuous phenomena, and train your scholar not to accept these phenomena as causes but as facts. I take a stone and pretend to place it in the air; I open my hand, the stone falls. I see Emile watching my action and I say, "Why does this stone fall?" What child will hesitate over this question? None, not even Emile, unless I have taken great pains to teach him not to answer. Every one will say, "The stone falls because it is heavy." "And what do you mean by heavy?" "That which falls." "So the stone falls because it falls?" Here is a poser for my little philosopher. This is his first lesson in systematic physics, and whether he learns physics or no it is a good lesson in common-sense. As the child develops in intelligence other important considerations require us to be still more careful in our choice of his occupations. As soon as he has sufficient self-knowledge to understand what constitutes his well-being, as soon as he can grasp such far-reaching relations as to judge what is good for him and what is not, then he is able to discern the difference between work and play, and to consider the latter merely as relaxation. The objects of real utility may be introduced into his studies and may lead him to more prolonged attention than he gave to his games. The ever-recurring law of necessity soon teaches a man to do what he does not like, so as to avert evils which he would dislike still more. Such is the use of foresight, and this foresight, well or ill used, is the source of all the wisdom or the wretchedness of mankind. Every one desires happiness, but to secure it he must know what happiness is. For the natural man happiness is as simple as his life; it consists in the absence of pain; health, freedom, the necessaries of life are its elements. The happiness of the moral man is another matter, but it does not concern us at present. I cannot repeat too often that it is only objects which can be perceived by the senses which can have any interest for children, especially children whose vanity has not been stimulated nor their minds corrupted by social conventions. As soon as they foresee their needs before they feel them, their intelligence has made a great step forward, they are beginning to know the value of time. They must then be trained to devote this time to useful purposes, but this usefulness should be such as they can readily perceive and should be within the reach of their age and experience. What concerns the moral order and the customs of society should not yet be given them, for they are not in a condition to understand it. It is folly to expect them to attend to things vaguely described as good for them, when they do not know what this good is, things which they are assured will be to their advantage when they are grown up, though for the present they take no interest in this so-called advantage, which they are unable to understand.