Thus, as the necessity, which makes two times two equal to four, or three angles of a triangle equal to two right ones, lies only in the act of the understanding, by which we consider and compare these ideas; in like manner, the necessity of power, which unites causes and effects, lies in the determination of the mind to pass from the one to the other. The efficacy or energy of causes is neither placed in the causes themselves, nor in the Deity, nor in the concurrence of these two principles; but belongs entirely to the soul, which considers the union of two or more objects in all past instances. 'Tis here that the real power of causes is placed, along with their connexion and necessity. I am sensible, that of all the paradoxes which I have had, or shall hereafter have occasion to advance in the course of this Treatise, the present one is the most violent, and that 'tis merely by dint of solid proof and reasoning I can ever hope it will have admission, and overcome the inveterate prejudices of mankind. Before we are reconciled to this doctrine, how often must we repeat to ourselves, _that_ the simple view of any two objects or actions, however related, can never give us any idea of power, or of a connexion betwixt them: _that_ this idea arises from the repetition of their union: _that_ the repetition neither discovers nor causes any thing in the objects, but has an influence only on the mind, by that customary transition it produces: _that_ this customary transition is therefore the same with the power and necessity; which are consequently qualities of perceptions, not of objects, and are internally felt by the soul, and not perceived externally in bodies? There is commonly an astonishment attending every thing extraordinary; and this astonishment changes immediately into the highest degree of esteem or contempt, according as we approve or disapprove of the subject. I am much afraid, that though the foregoing reasoning appears to me the shortest and most decisive imaginable, yet, with the generality of readers, the bias of the mind will prevail, and give them a prejudice against the present doctrine.