The lines, then, which I have laid down for my own guidance are these. My object is to seek for the principles and causes of mental evolution in man, first as regards the origin of human faculty, and next as regards the several main branches into which faculties distinctively human afterwards ramified and developed. In order as far as possible to gain this object, it has appeared to me desirable to take large or general views, both of the main trunk itself, and also of its sundry branches. Therefore I have throughout avoided the temptation of following any of the branches into their smaller ramifications, or of going into the details of progressive development. These, I have felt, are matters to be dealt with by others who are severally better qualified for the task, whether their special studies have reference to language, archæology, technicology, science, literature, art, politics, morals, or religion. But, in so far as I shall subsequently have to deal with these subjects, I will do so with the purpose of arriving at general principles bearing upon mental evolution, rather than with that of collecting facts or opinions for the sake of their intrinsic interest from a purely historical point of view. Finding that the labour required for the investigation, even as thus limited, is much greater than I originally anticipated, it appears to me undesirable to delay publication until the whole shall have been completed. I have therefore decided to publish the treatise in successive instalments, of which the present constitutes the first. As indicated by the title, it is concerned exclusively with the Origin of Human Faculty. Future instalments will deal with the Intellect, Emotions, Volition, Morals, and Religion. It will, however, be several years before I shall be in a position to publish these succeeding instalments, notwithstanding that some of them are already far advanced.