Happiness is based on a just discrimination of what is necessary, what is neither necessary nor destructive, and what is destructive. In the middle category, however—that of the unnecessary but undestructive, that of comfort, luxury, exuberance, etc.—they could perfectly well have central heating, subway trains, washing machines, and all kinds of marvelous devices not yet invented here, floating light-sources, fuelless power, a cure for the common cold. Or they could have none of that: it doesn’t matter.