Of these great divisions of our subject, the _Physiology of the Mind_, or the consideration of the regular series of phenomena which it presents, simply as states or affections of the mind, is that to which we are first to turn our attention. But, before entering on it, it may be useful to employ a few Lectures in illustrating the _advantages_, which the study of the mind affords, and the _principles of philosophizing_, in their peculiar application to it--subjects, which, though of a general kind, will, I trust, leave an influence that will be felt in all the particular inquiries in which we are to be engaged; preparing you, both for appreciating better the importance of those inquiries, and for prosecuting them with greater success. One very obvious distinction of the physical investigations of mind and matter, is, that, in intellectual science, the _materials_ on which we operate, the _instruments_ with which we operate, and the _operating agent_, are the same. It is the mind, endowed with the faculties of perception and judgment, observing, comparing, and classifying the phenomena of the mind. In the physics of matter, it is, indeed, the mind which observes, compares, and arranges; but the phenomena are those of a world, which, though connected with the mind by many wonderful relations of reciprocal agency, still exists independently of it--a world that presents its phenomena only in circumstances, over most of which we have no controul, and over others a controul that is partial and limited. The comparative facility, as to all external circumstances, attending the study of the mental phenomena, is unquestionably an advantage of no small moment. In every situation in which man can be placed, as long as his intellectual faculties are unimpaired, it is impossible that he should be deprived of opportunities of carrying on this intellectual study; because, in every situation in which he can be placed, he must still have with him that universe of thought, which is the true home and empire of the mind. No costly apparatus is requisite--no tedious waiting for seasons of observation. He has but to look within himself to find the elements which he has to put together, or the compounds which he has to analyze, and the instruments that are to perform the analysis or composition.