Hume opens section IV — entitled “Sceptical Doubts concerning the Operations of the Understanding” — by making a distinction between Relations of Ideas and Matters of Fact. The former are discovered and explored through “the mere operation of thought, without dependence on what is any where existent in the universe,” (15) while the latter are observable and — as Hume argues — deserve an investigation into their nature. Referring back to the three principles of association introduced in Section III, he asserts that “matters of fact seem to be founded on the relation of Cause and Effect” (16). The question then becomes one of discovering how we come to knowledge of cause and effect.
As one might expect at this point, Hume believes that the only way to understand cause and effect is via experience, rather than any sort of reasoning. He adds that we experience external objects only through their unique sensual qualities, and only know what is presented to us, rather than the causes which created them or the effects that might result from them (haecceities vs. quiddities? (thanks, Cheryl!)). Therefore, reason does not help us make connections between cause and effect; they are, for Hume, utterly distinct and can only be observed empirically.
His interrogation then turns to the process of inference that link statements such as ” I have found that such an object has always been attended with such an effect” and “I foresee, that other objects, which are, in appearance, similar, will be attended with similar effects” (22). Rather than grounding this inference in reason, he argues that “the most ignorant and stupid peasants,” (25) infants, and beasts — and even me, evidently: see my avocado remark in the last post — can make such inferences. His point here is not at all to belittle the process of making connections between cause and effect, but to take reason out of the equation. Any underlying connection between the cause and effect is hidden, and Hume argues that — from a philosophical point of view, though not necessarily from the perspective of everyday life — this relationship is likely to change at any time, thereby scrambling any ostensibly rational explanation. Readers of D&G will likely immediately make the same connections I’m making here between ontologies of Being and Becoming, as well as their celebration of the heroic schizo from Anti-Oedipus who scrambles all the codes and refuses to be oedipalized, triangulated.