Experience, causation, and induction › Why habit supplies what argument does not

Hume's Section V offers what he calls a skeptical solution. Someone encountering sequences of events for the first time would observe succession without immediately knowing what to expect. Repeated conjunction changes that person's response. The appearance of one event comes to carry thought toward another. Hume names this propensity custom or habit. He expressly says that naming it does not give an ultimate explanation of why the propensity exists. E 5.3–5.

Habit here means more than a routine someone has deliberately practiced. It is a principle through which experience shapes anticipation. The mind's transition becomes available without the person working through a fresh argument each time. Hume therefore gives a psychological account of how expectations arise while leaving the preceding argumentative difficulty in place. Explaining why someone makes an inference and providing a noncircular argument for that inference are different tasks.

This also changes how the skeptic should understand ordinary life. Hume says that nature will preserve the reasonings of common life despite abstract doubts about their foundation. Discovering that their basic transition lacks the proposed argumentative support does not extinguish the transition. The skeptical investigator still expects food to nourish and other people to respond. Hume's account includes the investigator among the human beings being investigated. E 5.2.

An imagined case makes the distinction practical. Someone learns that a colleague usually replies after lunch. After enough repetitions, an empty inbox in the morning stops being alarming. A habitual expectation has formed. Whether it is a good expectation on a particular day remains open to further evidence: perhaps the colleague is away. Hume's account of custom helps explain the expectation's formation. It should not be turned into advice to preserve it against new information.