This successor was J. F. McLennan, the direct opposite of his predecessor. Instead of the talented mystic, we have here the dry jurist; in place of the rank growth of poetical imagination, we find the plausible combinations of the pleading lawyer. McLennan finds among many savage, barbarian and even civilized people of ancient and modern times a type of marriage forcing the bride-groom, alone or in co-operation with his friends, to go through the form of a mock forcible abduction of the bride. This must needs be a survival of an earlier custom when men of one tribe actually secured their wives by forcible abduction from another tribe. How did this "robber marriage" originate? As long as the men could find women enough in their own tribe, there was no occasion for robbing. It so happens that we frequently find certain groups among undeveloped nations (which in 1865 were often considered identical with the tribes themselves), inside of which intermarrying was prohibited. In consequence the men (or women) of a certain group were forced to choose their wives (or husbands) outside of their group. Other tribes again observe the custom of forcing their men to choose their women inside of their own group only. McLennan calls the first exogamous, the second endogamous, and construes forthwith a rigid contrast between exogamous and endogamous "tribes." And though his own investigation of exogamy makes it painfully obvious that this contrast in many, if not in most or even in all cases, exists in his own imagination only, he nevertheless makes it the basis of his entire theory. According to the latter, exogamous tribes can choose their women only from other tribes. And as in conformity with their savage state a condition of continual warfare existed among such tribes, women could only be secured by abduction.