addition to the simple conception of it, I likewise maintain, that the belief of the existence joins no new ideas to those which compose the idea of the object.  When I think of God, when I think of him as existent, and when I believe him to be existent, my idea of him neither encreases nor diminishes.  But as it is certain there is a great difference betwixt the simple conception of the existence of an object, and the belief of it, and as this difference lies not in the parts or composition of the idea, which we conceive; it follows, that it must lie in the manner, in which we conceive it.

Suppose a person present with me, who advances propositions, to which I do not assent, that Caesar dyed in his bed, that silver is more fusible, than lead, or mercury heavier than gold; it is evident, that notwithstanding my incredulity, I clearly understand his meaning, and form all the same ideas, which he forms.  My imagination is endowed with the same powers as his; nor is it possible for him to conceive any idea, which I cannot conceive; nor conjoin any, which I cannot conjoin.  I therefore ask, Wherein consists the difference betwixt believing and disbelieving any proposition?  The answer is easy with regard to propositions, that are proved by intuition or demonstration.  In that case, the person, who assents, not only conceives the ideas according to the proposition, but is necessarily determined to conceive them in that particular manner, either immediately or by the interposition of other ideas.  Whatever is absurd is unintelligible; nor is it possible for the imagination to conceive any thing contrary to a demonstration.  But as in reasonings from causation, and concerning matters of fact, this absolute necessity cannot take place, and the imagination is free to conceive both sides of the question, I still ask, Wherein consists the deference betwixt incredulity and belief? since in both cases the conception of the idea is equally possible and requisite.

It will not be a satisfactory answer to say, that a person, who does not assent to a proposition you advance; after having conceived the object in the same manner with you; immediately conceives it in a different manner, and has different ideas of it.  This answer is unsatisfactory; not because it contains any falshood, but because it discovers not all the truth.  It is contest, that in all cases, wherein we dissent from any person, we conceive both sides of the question; but as we can believe only one, it evidently follows, that the belief must make some difference betwixt that conception to which we assent, and that from which we dissent.  We may mingle, and unite, and separate, and confound, and vary our ideas in a hundred different ways; but until there appears some principle, which fixes one of these different situations, we have in reality no opinion:  And this principle, as it plainly makes no addition to our precedent ideas, can only change the manner of our conceiving them.