Construction and destruction alike satisfy the will to power, but construction is more difficult as a rule, and therefore gives more satisfaction to the person who can achieve it. I shall not attempt to give a pedantically exact definition of construction and destruction; I suppose, roughly speaking, we construct when we increase the potential energy of the system in which we are interested, and we destroy when we diminish its potential energy. Or, in more psychological terms, we construct when we produce a predesigned structure, and we destroy when we liberate natural forces to alter an existing structure, without being interested in the resulting new structure. Whatever may be thought of these definitions, we all know in practice whether an activity is to be regarded as constructive or destructive, except in a few cases where a man professes to be destroying with a view to rebuilding and we are not sure whether he is sincere. Destruction being easier, a child’s games usually begin with it, and only pass on to construction at a later stage. A child on the sand with a pail likes grown-up people to make sand-puddings, and then knock them down with his spade. But as soon as he can make sand-puddings himself, he delights in doing so, and will not permit them to be knocked down. When a child first has bricks, he likes to destroy towers built by his elders. But when he has learnt to build for himself, he becomes inordinately proud of his performances, and cannot bear to see his architectural efforts reduced to a heap of ruins. The impulse which makes the child enjoy the game is exactly the same at both stages, but new skill has changed the activity resulting from the impulse. The first beginnings of many virtues arise out of experiencing the joys of construction. When a child begs you to leave his constructions undestroyed, you can easily make him understand that he must not destroy other people’s. In this way you can create respect for the produce of labour, the only socially innocuous source of private property. You also give the child an incentive to patience, persistence, and observation; without these qualities, he will not succeed in building his tower to the height upon which he had set his heart. In play with children, you should only construct yourself sufficiently to stimulate ambition and to show how the thing is done; after that, construction should be left to their own efforts.