_Theory of Mahan._--Mahan, in his Intellectual Philosophy, carries out the suggestion of Dr. Brown, and makes the emotion awakened in common by two or more objects, the sole law, or ground of association. One object recalls an other only by means of the feeling or state of mind common to both. _This View questionable._--That this is the philosophy of the suggesting principle in those cases in which two objects have not previously coëxisted in the mind--that is, in cases of suggestion, and not of _association_ properly--I am disposed to admit, but that it is the philosophy of _association_, strictly speaking, that it is the reason why objects which have been viewed together by the mind should afterward recall each other, is to be questioned. It seems to be an established law of mental action that objects once viewed in connection by the mind, afterward retain that connection. This is a grand and simple law of thought. I doubt whether any explanation can make it more simple, whether any thing is gained by calling in the influence of emotion to account for it. The emotion may, or may not, be the cause why objects, once coëxistent in the mind, recall each other. It is enough that the simple law of previous coëxistence, as now stated, covers the whole ground, and accounts for all the phenomena of mental association. _The same Rule given by Aristotle._--Long before the days of Brown and his successors, this same law had suggested itself to one of the closest thinkers, and most acute observers of mental phenomena, whom the world has ever seen, as a principle comprehensive of all the specific laws of association. _Aristotle_--as quoted by Hamilton--expresses the rule in the following terms: _Thoughts, which have at any time, recent or remote, stood to each other in the relation of coëxistence, or immediate consecution, do, when severally reproduced, tend to reproduce each other._ Under this general law he includes the specific ones of similars, contraries, and coädjacents, as comprehending all the possible relations of things to each other.