A population that is found anywhere on British territory falls, roughly speaking, into two categories. The same thing is, in general, true in other countries of the world. The two categories, of course, include, on the one hand, persons who are aliens and, on the other, persons who are said to be of the nationality of the country involved. In Great Britain, aliens are, for many practical purposes, in a position that is not unlike the position of persons of British nationality. If aliens are present on British territory, they may move about freely and peaceably, indistinguishable in most respects from the British. Nevertheless, aliens are not in reality members of the British nation. They may, it is true, with comparative ease become British through naturalization; but, as long as they are aliens, they are to be distinguished from the bulk of persons of British nationality.
Nationality and nation, like so many of the concepts with which the student of government is concerned, are at the same time familiar concepts in common usage and concepts of a technical nature. This is to say that they share with most concepts encountered in political science the possession of both a non-legal and a legal aspect. The two aspects are, of course, reciprocally related. The non-legal in part determines and in part is determined by the legal. Thus, for example, in respect of nationality, a wholly legal idea of the phenomenon is too rigid and narrow, a wholly non-legal concept of it too vague.
The non-legal aspect of nationality may be said to be its common-sense, its general, its less definite and rigid, its moral, or its sentimental aspect. From this point of view, accurate definition of nationality would seem to be for practical purposes