It is important to keep steadily in view the fact, that the New Testament invariably represents possession as consisting in the action of a stronger mind on a weaker one. The influence which the demon exerted on the bodily organs might have been effected through the agency of the man himself. It is never described as involving a visible manifestation of the demon, but his action is one which is purely mental and spiritual. His presence and his departure were simply judged of by their effects. It follows, therefore, that the denial of the possibility of an influence of this kind must rest on a very wide principle. It cannot be confined to such action alone, but must go to the extent of denying the possibility of the action of all spiritual beings on the mind of man. The only principle on which the denial can rest is, that our mental science has so far succeeded in analyzing all the past and present operations of the human mind, that it is justified in affirming that they all originate entirely within the mind itself; and are never brought about by an action on it from without by any invisible agent. If this is the principle on which the denial rests, it will be equally valid to exclude the action of God on our minds, as well as that of all other invisible beings. It will doubtless be urged that it is only intended to deny the action of invisible evil beings. But if it is true that our mental philosophy has ascertained that all our thoughts originate either in the mind itself, or in the mind acted on by external nature, or by other men, the principle must be valid for proving that all other spiritual agency exerted on the mind is impossible, and that all supposed instances of it are delusions. It is impossible on this principle to exclude the evil agency, and not to exclude the good also.