When however we come to the so-called group marriage, using the term in its original sense of limited promiscuity, we are dealing with an entirely different state of things, and it is difficult to see any justification for the use of the term marriage in this connection at all.  By group marriage is meant a condition only removed from absolute promiscuity by the existence of age-classes or of two or more exogamous classes in the community; it demands no special ceremonies prior to the individual union[141], it permits this union to be dissolved at will, and it consequently confers no rights on either of the parties to it, other than perhaps the right to the produce, or some of the produce, of each other’s labour.

If the confusion did not extend beyond the terminology, the advance of knowledge would perhaps be but little impeded; but experience shows that confusion in terminology is apt to go hand in hand with confusion in ideas.  As will be shown later, this seems to be particularly true of investigations into the history of marriage and sexual relationships.  It seems desirable therefore to clear the way by classifying the ideas with which we have to deal, and by defining the terms corresponding to them.

Before classifying the various forms of sexual relationships, it may be well to say a few words on the definition of marriage in general.  Dr Westermarck has defined it from the point of view of natural history as a more or less durable connection between male and female, lasting beyond the mere act of propagation till after the birth of the offspring.

It may not be possible to propose a better definition from the point of view selected by Dr Westermarck, which is certainly the one from which anthropology must regard sexual relationships.  At the same time it is not entirely free from objection.  In the first place we are employing the word marriage in a sense which has but little in common with its ordinarily accepted meaning.  Suppose, for example, we are dealing with marriage in Europe, it is confusing to be compelled by our definition to regard as a marriage the faux menage, not to speak of the not uncommon fairly permanent unions in which there is no common residence.  Such monogamous relationships may be, technically speaking, marriages, in Dr Westermarck’s sense, but it seems desirable to make use of some other term for them and reserve marriage for the unions sanctioned by legal forms.  Or take the union of two people, each of whom has prior matrimonial engagements.  Such a union may, as the records of the divorce court show, be anything but impermanent; but it does not make for clearness to call such an union marriage.  Let us take a third example—­a New Hebridean girl purchased, or in Upa stolen, for the use of the young men, who, of course, reside in their club-house.  If any of the bachelors there resident chooses to recognise her children, they are regarded as his children; if not, they are supported by the whole of the residents