Notes on Hume's Treatise
by G. J. Mattey
PART III. OF KNOWLEDGE AND PROBABILITY
§ VIII. Of the causes of belief.
From what principles is a belief derived?
A general maxim is that "when any impression becomes present to us, it not only transports the mind to such ideas as are related to it, but likewise communicates to them a share of its force and vivacity." An example is when a picture of a friend reminds me of him, it also fires up my passions concerning them. When there is a bad image, we would rather think of the friend directly rather than to have our ideas dulled. The ceremonies of the Roman Catholic religion have the same effect: the statues quicken the fervor of their devotions. Conclusion: "the effect of resemblance in enlivening the idea is very common."
Other "experiments" regarding contiguity might be adduced. Distance diminishes the intensity of the ideas, though only the impression can make them really lively.
Causation works the same way. Relics of saints are end-points of a short causal chain, and as such they enliven our ideas. "This phaenomenon clearly proves, that a present impression with a relation of causation may enliven any idea, and consequently produce belief or assent, according to the precedent definition of it."
Our reasoning from cause to effect is enough to prove that a present impression with a transition is by itself sufficient to enliven belief. "'tis certain we must have an idea of every matter of fact, which we believe. 'tis certain that this idea arises only from a relation to a present impression. 'tis certain, that the bel ief super-adds nothing to the idea, but only changes our manner of conceiving it, and renders it more strong and lively. The present conclusion concering the influence of relation is the immediate consequence of all these steps; and every step appears to me sure and infallible."
The constitution of the object has no influence on the belief that we form. The present impression is all we have to serve as the cause of the idea, since "the phenaenomenon of belief . . . is merely internal." The powers of bodies are "entirely unknown." So our investigation must turn to the present impression.
The impression does not produce belief on its first presentation, but only after it has been severally observed and constantly conjoined to another object.
Moreover, the belief arises immediately, "without any new operation of the reason or imagination." One is never conscious of such an operation, nor can one find a basis for it in the subject. CUSTOM is the origin of the belief, and it is defined as whatever procedes from a past repetition without any new reasoning or conclusion. "When we are accustom'd to see two impressions conjoin'd together, the appearance or idea of the one immediately carries us to the idea of the other."
Is anything more required besides the impression and the transition to produce belief? To answer this question, we change the starting point from an impression to an idea. When this is done, there is still a transition, but no belief. "A present impression, then, is absolutely requisite to this whole operation; and when after this I compare an impression with an idea, and find that their only difference consists in their different degrees of vivacity, I conclude upon the whole, that belief is a more vivid and intense conception of an idea, proceeding from its relation to the present impression."
All probable reasoning is a species of sensation: a sentiment in the person, just as are music and poetry. Preference given to a conclusion of one argument over that of another is no more than a feeling of the superiority of the preferred inference. "Objects have no discoverable connexion together; nor is it form any other principle but custom operating upon the imagination, that we can draw any inference from the appearance of the one to the existence of the other."
The past experience need not be taken notice of, or it may be entirely unknown. "The custom operates before we have time for reflexion" in the case of a man who stops before a river, without perusing the casual chain from water to sinking to suffocating. The operation is secret. So we don't reason through a principle, "that instances of which we have no experience, must necessarily resemble those, of which we have." No reflection on this principle is needed.
This reflection may assist us in more rare and unusual cases, and in oblique and artificial reasonings it may be appealed to directly, bypassing custom, as in inference from a single controlled experiment, where no custom could arise. Still, we presume in the inference the general principle that was the result of custom: "that like objects, plac'd in like circumstances, will always produce like effects."
There is some ambiguity in common language in the words 'strong' and 'lively.' An objection may be made that an idea may be the source of reasoning, especially given the principle that ideas are copies of impressions. An idea, strong and lively enough, may produce belief even though the impression it copies is forgotten. In that cases, where does the vivacity of the consequent idea come from? Answer: from the idea itself, not considered as the representation of that impression. "The idea here supplies the place of an impression, and is entirely the same, so far as regards our present purpose."
The vivacity of the memory of an idea vis-a-vis the loose conceptions of the imagination is explained in the same manner. The memory offers an idea of the action of the mind which is lacking in loose conception. This action is a "certain je-ne-scai-quoi , of which 'tis impossible to give any definition or description, but which every one sufficiently understands."