Pan-Americanism and imperialism appear to be mutually exclusive. Whether they are so in effect is a matter of definition. Neither term in current usage conveys a precise meaning. Pan-Americanism fails because it has not yet emerged into a distinct and easily recognizable form, and imperialism because it has evolved in the course of history through a variety of forms from which a doubtful choice must be made. In the one case the problem is to decide what meaning, and in the other, which meaning. The "what" is the more difficult to determine, since new concepts such as Pan Americanism acquire meaning with time and circumstance. It is not strange, therefore, that the attempts at formal definition have thus far proved unsatisfactory. Not even the genus to which Pan-Americanism belongs has been agreed upon. One author calls it an advocacy, another an idea, another a sentiment, and sti l others an aspiration, a tendency, or a doctrine. Obviously it does not fall indifferently into all these categories. If it is a sentiment merely, it is less than a doctrine; if it is a doctrine it is more than a tendency; and to call it a tendency is not the same as to say it is an aspiration or an idea. Moreover, none of these classifications when considered separately seems to fit the case.