There are two classes of men who occupy themselves in observations on mental functions, frequently working widely apart from each other. These are, the metaphysicians, who investigate the phenomena of mind apart from anatomical or physiological facts, and the physiologists, who keep as exclusively to their own labours. Neither of these classes of men have as yet formed any philosophical system of the mental powers, and other functions of the brain; and it may be safely asserted that it is only by a combination of metaphysics and physiology that we can advance any considerable steps in our knowledge. The philosophical Reid, whose greatest disciple was Sir William Hamilton, stated many years ago, in his “Essays on the Powers of the Human Mind,” that they are “so many, so various, and so connected and complicated in most of their operations, that there never has been any division of them proposed which is not liable to considerable objections.” All the classifications made by metaphysicians differ materially from each other, and what was true in Reid's time is true now. We have a different race of metaphysicians from those who flourished years ago, different from Reid, Dugald Stewart, and Brown, but as yet we seem no nearer than we were to a systematic and comprehensive classification of mental faculties, or more properly, of the functions of the brain. I would not say that no progress has been made, for a vast mass of facts has been accumulated, and careful observations have been made, which will be available at some future period for a scientific and philosophical classification.