The substantial difference between the peaceable and the predatory phase of culture, therefore, is a spiritual difference, not a mechanical one. The change in spiritual attitude is the outgrowth of a change in the material facts of the life of the group, and it comes on gradually as the material circumstances favourable to a predatory attitude supervene. The inferior limit of the predatory culture is an industrial limit. Predation can not become the habitual, conventional resource of any group or any class until industrial methods have been developed to such a degree of efficiency as to leave a margin worth fighting for, above the subsistence of those engaged in getting a living. The transition from peace to predation therefore depends on the growth of technical knowledge and the use of tools. A predatory culture is similarly impracticable in early times, until weapons have been developed to such a point as to make man a formidable animal. The early development of tools and of weapons is of course the same fact seen from two different points of view. The life of a given group would be characterised as peaceable so long as habitual recourse to combat has not brought the fight into the foreground in men's every day thoughts, as a dominant feature of the life of man. A group may evidently attain such a predatory attitude with a greater or less degree of completeness, so that its scheme of life and canons of conduct may be controlled to a greater or less extent by the predatory animus. The predatory phase of culture is therefore conceived to come on gradually, through a cumulative growth of predatory aptitudes habits, and traditions this growth being due to a change in the circumstances of the group's life, of such a kind as to develop and conserve those traits of human nature and those traditions and norms of conduct that make for a predatory rather than a peaceable life. The evidence for the hypothesis that there has been such a peaceable stage of primitive culture is in great part drawn from psychology rather than from ethnology, and cannot be detailed here. It will be recited in part in a later chapter, in discussing the survival of archaic traits of human nature under the modern culture. Chapter Two ~~ Pecuniary Emulation In the sequence of cultural evolution the emergence of a leisure class coincides with the beginning of ownership. This is necessarily the case, for these two institutions result from the same set of economic forces. In the inchoate phase of their development they are but different aspects of the same general facts of social structure.