Before I proceed to consider the diseases of the mind, I shall briefly mention its different faculties and operations.
Its faculties are, Understanding, Memory, Imagination, Passions, the principle of Faith, Will, the Moral faculty, Conscience, and the sense of Deity.
Its principal operations, after sensation, are Perception, Association, Judgment, Reasoning and Volition. All its subordinate operations, which are known by the names of Attention, Reflection, Contemplation, Wit, Consciousness, and the like, are nothing but modifications of the five principal operations that have been mentioned.
The faculties of the mind have been called, very happily, internal senses. They resemble the external senses in being innate, and depending wholly upon bodily impressions to produce their specific operations. These impressions are made through the medium of the external senses. As well might we attempt to excite thought in a piece of marble by striking it with our hand, as expect to produce a single operation of the mind in a person deprived of the external senses of touch, seeing, hearing, taste and smell.
