Experience, causation, and induction › The materials of thought

Hume begins his account of ideas with a distinction between experiencing something and thinking about it. Feeling heat differs from remembering heat. Anger as you undergo it differs from calmly recalling an earlier quarrel. In Section II, he calls the more forceful perceptions impressions and the less forceful ones ideas. Impressions include feelings and desires as well as sensory experiences; they are not restricted to messages from the eyes and ears. Ideas include thoughts and recollections. E 2.1–3.

The imagination can combine materials in ways that experience has never presented together. Hume's example is a golden mountain: someone acquainted with gold and mountains can join their ideas. Creative thought therefore need not copy a complete scene. His general proposal is that its simpler materials originate in impressions, even when their eventual combinations are unfamiliar. This gives him a method for inspecting obscure philosophical language. Ask which experience supplies the idea the word supposedly expresses. A fluent definition does not settle that question. E 2.5–9.

Hume also supplies a difficulty for his own proposal. Imagine someone familiar with a graduated series of blue shades except for one missing shade. He thinks the person could supply the missing idea despite never having received that precise impression. He treats this as a singular exception rather than a reason to abandon the general maxim. The exception deserves to stay visible: presenting his empiricism as a rule he allows no counterexample would misrepresent his argument. E 2.8.

For a modern illustration, imagine a discussion in which a manager explains every success by invoking a team's mysterious "energy." Hume's method invites clarification. Does the speaker mean enthusiasm, rapid responses, willingness to cooperate, or something else that can be described through experience? The question does not prove that every useful concept must name an observable object. It asks what content a speaker actually has available when a familiar word seems to explain everything.