There are certain evident priorities among impulses, some of which have been studied in various ways by economists under the headings of primary wants and secondary wants. Some needs or impulses must be satisfied in order that others may be possible. We must eat, drink, sleep, breathe, protect ourselves and carry on an immense physiological business as a condition for any further activities. Some of these impulses, breathing, for example, can be satisfied directly, but most of them involve us in complicated cycles of instrumental labour. Man for the most part must exert himself half his life to satisfy even the primitive needs, and these activities, failing other means of reaching the same ends, share their priority. In their turn they involve as conditions a group of impulses, whose satisfaction becomes only second in importance to physiological necessities, those, namely, upon which communication and the ability to co-operate depend. But these, since man is a social creature, also become more directly necessary to his well-being. The very impulses which enable him to co-operate in gaining his dinner would themselves, if not satisfied, wreck by their mere frustration all his activities. This happens all through the hierarchy. Impulses, whose exercise may have been originally only important as means, and which might once have been replaced by quite different sets, become in time necessary conditions for innumerable quite different performances. Objects, again, originally valued because they satisfy one need, are found later to be also capable of satisfying others. Dress, for example, appears to have originated in magical, ‘life-giving,’ ornaments[22], but so many other interests derive satisfaction from it that controversy can still arise as to its primitive uses.