_Points of Difference between this Theory and Reid's._--The system, as thus stated, differs in some respects materially from the doctrine of perception advanced by Dr. Reid, and generally adopted since his time by the English and Scotch philosophers. According to Hamilton, perception is not, as held by Reid and others, the _conception_ of an object _suggested_ by sensation, but the direct cognition of something. We do not merely _conceive_ of the object as existing, and _believe_ it to exist, we _know_ it and _perceive_ it to exist. Nor does sensation precede, and perception follow, as generally stated, but the two are, in time, conjunct, coëxistent. Nor do we perceive the secondary qualities of bodies, as such, but only _infer_ them from our sensations. Neither do we perceive distant objects through a medium, as usually held, but what we perceive is either the organism itself, as affected thus and thus, or what is directly in contact with it, as affecting and resisting it. Extension and externality, again, are not first learned by _touch_, as Reid holds, and most subsequent writers, both English and American, but in other ways; the former, by the perception of the primary qualities of our own organism, as the seat of sensations distinct from other sensations elsewhere localized; the latter, by the resistance which we experience to our own locomotive force. Finally, sensation proper is not, as with Reid and others, an affection purely of the mind, but of mind and body as complex. Its subject is as much one as the other. INTELLECTUAL FACULTIES. PART SECOND THE REPRESENTATIVE POWER GENERAL OBSERVATIONS. _Nature of this Power--Its various Forms._--It is in the mind's power to conceive or represent to itself an object not at the time present to the senses. This may take place in several forms. There may be the simple reproduction in thought of the absent object of sense. There may be, along with the reproduction or recurrence of the object, the _recognition_ of it as a former object of sensation or perception. There may be the reproduction of the object not as it is, or was, when formerly perceived, but with variations, the different elements arranged and combined not according to the actual and original, but according to the mind's own ideals, and at its will. This latter form of conception is what is usually termed imagination--while the general term memory, as ordinarily employed, is made to include the two former. While using the term in this general sense, we may properly distinguish, however, between mental reproduction, and mental recognition, the latter being strictly the office of memory.