Every man has a number of purposes and desires, some purely personal, others of a sort which he can share with many other men. Most men desire money, for example, and most ways of growing rich involve co-operation with some group. The group concerned depends upon the particular way of growing rich. For most purposes two different firms in the same business are rivals, but for purposes of a protective tariff they co-operate. Money, of course, is not the only thing for which people fall into groups of a political kind. They are organised into churches, brotherhoods, learned societies, freemasons, and what not. The motives which lead men to co-operate are many: identity of interest is one; identity of opinion is another; and ties of blood are yet a third. The Rothschild family co-operated owing to ties of blood. They did not need formal articles of incorporation, because they could trust each other, and a great part of their success was due to the fact that there was a Rothschild in every important financial centre in Europe. A form of co-operation based upon identity of opinions is to be seen in the philanthropic work

of the Quakers after the war. They were able to work together easily because of their similarity of outlook. Ties of self-interest are the basis of such organisations as joint-stock companies and trade-unions.