Since these groups of impulses have shown themselves to play a part of such importance in human mind and human conduct, it is not unnatural that, having completed our review of their manifestations, we should feel some curiosity as to the manner in which they have come to play this part in the course of the past history of the human race and as to the nature of the influence which they have exerted on this history. Unfortunately in the present state of our knowledge it would not seem possible to gratify this curiosity except in a very partial, unsatisfactory and uncertain manner. The psychological mechanisms with which we have been dealing have themselves, for the most part, been too recently discovered to have as yet been adequately correlated, or brought into connection, with the relevant facts of anthropological, ethnographical or biological science. The data from these latter sources are moreover, in spite of much diligent research in recent years, still in many important respects too incomplete to afford a satisfactory basis for such correlation. As a consequence of these conditions, it is to be feared that any attempt that we may make to exhibit the psychical tendencies with which we have been concerned, in their bearings upon early human history, or to explain their origin in the light of this history or of the general conditions of human life and mind, will result in little more than a restatement of our psychological principles from a slightly different point of view. Nevertheless the attempt may be worth making. A summary of some of the main implications of our psychological knowledge in this field may perhaps not seem amiss--especially in view of the astonishing and unlooked-for character of much of this knowledge--and if we succeed in establishing a few connections between our psychological data and the related facts of anthropology or biology, these may perhaps serve as starting points--to be either proved or else corrected--for subsequent enquiries based on a more sound foundation. The reader will understand therefore that, in so far as in the present and the two succeeding chapters there is anything that is not--explicitly or implicitly--contained in what we have already said, we shall have left the region of comparative certainty afforded by the results of observation and induction, and shall be travelling for the most part on the unsure ground of speculation--speculation that can be justified only on the plea of natural curiosity, and by the hope of opening up a few vistas which may be more fully surveyed by better equipped workers in the future. [Sidenote: The hate tendencies to some extent inevitable]