Notes on Hume's Treatise
by G. J. Mattey
PART III. OF KNOWLEDGE AND PROBABILITY
§ VII. Of the nature of the idea or belief.
"The idea of an object is an essential part of the belief of it, but not the whole." We conceive of many ideas we do not assent to.
To conceive of an idea as existent is not to add to or alter it. Existence is not separable from the idea itself. Not only is the conception of existence no addition, but the belief of the existence adds nothing. There is a difference between the two, which can only be found "in the manner in which we conceive the object."
With respect to propositions proved by intuition or demonstration, the person is necessarily determined to conceive the idea in the manner he does. But this does not help in cases of reasoning from causation. One can conceive the object both incredulously (not believing) and credulously (believing).
We can run through things any which way, but the only factor that could constitute a belief is the manner of conceiving them.
Between impressions and ideas, the only difference is vivacity. To vary the content of the idea would be to represent a different object or impression. Thus the only difference between an idea which is a belief and one which is not is also vivacity. An analogy is made with colors, where "a particular shade of any colour may acquire a new degree of liveliness or brightness without any other variation." But where there is a variation, there is a new shade of color. "An opinion, therefore, or belief may be most accurately defin'd, A LIVELY IDEA RELATED TO OR ASSOCIATED WITH A PRESENT IMPRESSION."
Fn. 1. There is a systematic error in the classification of acts of the understanding into conception (simple survey of ideas), judgment (separating and uniting of ideas), and reasoning (separating and uniting via intermediaries). Two points can be made about this distinction. 1) Some judgments involve no separation or uniting, e.g. 'God exists.' 2) Causal reasoning is a convincing form of reasoning, but no intermediaries are involved. All three alleged forms resolve into the first. The only difference is that we sometimes attach a belief to the conception. Belief is a strong and steady conception which "approaches in some measure to an immediate impression."
A summary of the argument to date is given. An impression is the starting point, on pain of regress. Reason does not inform us of the existence of any thing, so custom is required. So belief in casual reasoning is the production of a lively idea related to the present impression "by custom or a principle of association." Belief is "somewhat more than a simple idea," being "a lively idea produc'd by a relation to a present impression, according to the foregoing definition."
To justify this "definition," appeal is made to "every one's feeling and experience." Assent is contrasted with "the loose reveries of a castle-builder." Reading a book as a history as opposed to reading another as a romance produces "a more lively conception of all the incidents." One receives entertainment from the romance only due to the style and ingenuity of the composition, not because of our interest in the characters as such (as in history, where we form conceptions of their features, friends, etc.).