The necessity of commencing with the co-ordination of ideas is not merely due to the fact that the relations of these, being more simple and more susceptible of demonstration, form a useful logical preparation for the remainder of the task. On closer examination we find a more important, though less obvious reason. If this first portion of the work be once efficiently performed, it is the foundation of all the rest. In what remains no very serious difficulty will occur, provided always that we content ourselves with that degree of completeness which the ultimate purpose of the system requires. To give such paramount importance to this portion of the subject may seem at first sight inconsistent with the proposition just laid down, that the strength of the intellectual faculties is far inferior to that of the other elements of our nature. It is quite certain that Feeling and Activity have much more to do with any practical step that we take than pure Reason. In attempting to explain this paradox, we come at last to the peculiar difficulty of this great problem of human Unity. The first condition of unity is a subjective principle; and this principle in the Positive system is the subordination of the intellect to the heart: Without this the unity that we seek can never be placed on a permanent basis, whether individually or collectively. It is essential to have some influence sufficiently powerful to produce convergence amid the heterogeneous and often antagonistic tendencies of so complex an organism as ours. But this first condition, indispensable as it is, would be quite insufficient for the purpose, without some objective basis, existing independently of ourselves in the external world. That basis consists for us in the laws or Order of the phenomena by which Humanity is regulated. The subjection of human life to this order is incontestable; and as soon as the intellect has enabled us to comprehend it, it becomes possible for the feeling of love to exercise a controlling influence over our discordant tendencies. This, then, is the mission allotted to the intellect in the Positive synthesis; in this sense it is that it should be consecrated to the service of the heart.