Notes on Hume's Treatise
by G. J. Mattey
PART III. OF KNOWLEDGE AND PROBABILITY
§ II. Of probability; and of the idea of cause and effect .
This section will explain those three relations which may be absent or present though the idea remains the same.
Reasoning involves the comparison of ideas, but when both are present, there is perception only. Thus there is no reasoning regarding our "observations" concerning identity and relations of time and place. Only causation does not require the presence of both objects, but allows us from the presence of one to "give us assurance" of the existence of another.
Cause and effect is what governs our reasoning about identity and spatio-temporal relations. If we think objects are invariably adjacent or separate, it is because we think there is a secret cause connecting them or separating them. With identity, perfect resemblance is not enough, we need a cause connecting this perception to a pervious one.
We cannot reason "justly" without an understanding of our idea of cause, and hence finding its origin "and examining the primary impression, from which it arises."
It is no one quality, for there is no single quality which belongs to all beings; yet any one can be deemed cause or effect. So we must look to a relation among objects.
Every object considered as cause or effect is contiguous. "Commonly" it is found that objects appearing to act at a distance are linked in a chain of contiguous objects. We presume the connection to exist even when we do not find one. [Cf. Newton.] So CONTIGUITY will be considered essential to the relation of causation.
Also essential is the relation of PRIORITY in time of the cause before the effect. Some claim that causality can be contemporaneous. But, 1) experience apparently contradicts this, and 2) an inference to this conclusion may be given. Claim: If one cause were contemporaneous with its effect, all would be. This is because any one cause which is delayed is not a proper cause, according to the maxim that "an object, which exists for any time in its full perfection without producing another, is not its sole cause." Generalizing, "if one cause were co-temporary with its effect, and this effect with its effect, and so on," the succession requisite for time would be abolished. At any rate, we can suppose the requirement of priority to be correct, as it is of no great moment.
Consideration of a single instance yields nothing more than contiguity and precedence. It does no good to say that the first produces the second, since explanation of production would invoke causation, resulting in circularity.
But we cannot rest with contiguity and succession, since they may exist without our considering that there is a causal relation. We must add a NECESSARY CONNEXION, a relation of far more importance than the first two.
What impressions give rise to the idea of a necessary connection? It is no known quality, and only the relations of contiguity and succession may be found. It would be wrong to back off the previously established principle that ideas are copies of impressions. So we must grope blindly for one, looking elsewhere for hints.
"First, For what reason we pronounce it necessary, that every thing whose existence has a beginning, shou'd also have a cause.
"Secondly, Why we conclude, that such particular causes must necessarily have such particular effects; and what is the nature of the inference we draw from the one to the other, and of the belief we repose in it."
Although emphasis is on the relation derived from impressions of sensation, those of reflection admit no less of the relation of cause and effect, connecting our passions.