The third lecture, on Positivism, completes the first group, and forms, as it were, a kind of useful appendix to the other two. Here we have the investigation of a special system,--a system that professes to be based on positive and observed phenomena, and claims to extricate the mental study of man from metaphysics and abstractions, and to place it in the realm of the realizable and the positive. Such a system, though neither now prevailing to any extent, nor ever likely to become prevalent or popular, is still worthy of attention, as it stands in close connection with current materialistic conceptions, and suggests some instructive contrasts to Pantheism. In the latter system we have, at any rate, some idea of pervading Deity; but in Positivism, if we understand the system aright, God, and all conceptions of God, are not so much denied as simply and entirely ignored. If Pantheism be deemed fascinating, Positivism will appear to most minds utterly repellent: still it is a system that claims some distinguished men among its professed exponents, and perhaps a larger number than we may suppose of conscious or unconscious adherents. It may therefore well claim from us investigation, and, in the position it occupies in the order of these lectures, may fairly be considered to be in its right place. We have dwelt upon the first group of the lectures, as both the position and the importance of the subjects considered in it have seemed to require a fuller notice. On the remaining groups we may speak more briefly, as their connection and the special subjects on which they treat are much more self-explanatory.