David Hume (1711-1776) is one of the British Empiricists of the Early Modern period, along with John Locke and George Berkeley. Although the three advocate similar empirical standards for knowledge, that is, that there are no innate ideas and that all knowledge comes from experience, Hume is known for applying this standard rigorously to causation and necessity. Instead of taking the notion of causation for granted, Hume challenges us to consider what experience allows us to know about cause and effect.
Hume shows that experience does not tell us much. Of two events, A and B, we say that A causes B when the two always occur together, that is, are constantly conjoined. Whenever we find A, we also find B, and we have a certainty that this conjunction will continue to happen. Once we realize that “A must bring about B” is tantamount merely to “Due to their constant conjunction, we are psychologically certain that B will follow A”, then we are left with a very weak notion of necessity. This tenuous grasp on causal efficacy helps give rise to the Problem of Induction–that we are not reasonably justified in making any inductive inference about the world. Among Hume scholars it is a matter of debate how seriously Hume means us to take this conclusion and whether causation consists wholly in constant conjunction.
This article examines the empirical foundations that lead Hume to his account of causation before detailing his definitions of causation and how he uses these key insights to generate the Problem of Induction. After explicating these two main components of Hume’s notion of causation, three families of interpretation will be explored: the causal reductionist, who takes Hume’s definitions of causation as definitive; the causal skeptic, who takes Hume’s problem of induction as unsolved; and the causal realist, who introduces additional interpretive tools to avoid these conclusions and maintains that Hume has some robust notion of causation.