Is it possible in a single formula to express everything that is requisite for a practical international language? I think so, and a brief consideration of the two reasons which prevent us from choosing one of the natural languages as an international language will enable me to arrive very quickly at this formula. The first reason is, that such a procedure would unfairly benefit one nation at the expense of all the others and would infringe the fundamental principle of neutrality, which is necessary in all international affairs. The second reason is, that every language is too difficult for foreigners. All existing languages swarm with difficulties of pronunciation, spelling, grammar, vocabulary, and especially idiom. It is very seldom that a foreigner succeeds, even after years of study, in learning a language sufficiently well to avoid occasionally making one of those mistakes which instantly betray his origin to the natives; it may be a false stress, or a word employed with an almost imperceptibly different shade of meaning, or placed in a position in a sentence where the native would never place it, or, finally, a phrase which, though logically correct, is nevertheless not permitted by the usage of the language. On account of their innumerable relationships and associations, which is indeed what makes them so dear to the nations that employ them, all natural languages are extraordinarily difficult, and therefore unsuitable for the purpose of international intercourse. We require, accordingly, a language which shall be not only neutral, but also as easy as possible: easy to learn, easy to use, and easy to understand. These considerations bring me to the sought-for formula, which we may express in a form similar to the celebrated ethical dictum of Hutcheson and Bentham ("That action is best which accomplishes the greatest happiness for the greatest number"):-- _That international language is best which offers the greatest facility to the greatest number._ It may be objected, however, that facility is a subjective idea: what is easy for one is not always easy for another. Quite so, and it is exactly that observation which will serve us as a guide in the investigation of the important conclusions which may be drawn from our fundamental principle.