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mer advocates had not contemplated. But it is a singular fact, as stated by Dr. Reid, that nearly all philosophers, from Plato to Mr. Hume, agree in maintaining that the mind does not perceive external things themselves, but only their ideas, images, or species. This doctrine was founded upon the maxim that mind cannot act where it is not present ; and we find one writer only, who, admitting the maxim, called in question the application of it so far as to maintain that the mind, in perceiving external things, leaves the body, and comes into contact with the objects of its perception. Such speculations ought to be entirely banished from the science of mind, as not only useless and unprofitable, but as referring to things entirely beyond the reach of the human faculties, and therefore contrary to the first principles of philosophical investigation. To the same class we are to refer all speculations in regard to the essence of mind, the manner in which thought is produced, and the means by which the intercourse is carried on between the mind and external objects. These remarkable functions were at one time explained by an imaginary essence called the animal spirits, which were supposed to be in constant motion, performing the office of messengers between the brain and tha organs of sense. By another class of philosophers, of no very ancient date, thinking was ascribed to vibrations in the particles of the brain. The communication of perceptions from the senses to the mind has been accounted for in the same manner by the motions of the nervous fluid, by vibrations of the nerves, or by a subtile essence, resembling electricity or galvanism. The mind, again, has been compared to a cameraobscura, to a mirror, and to a storehouse. In opposition, however, to all such hypotheses, which ...
