---
title: Causation
sort: 120
section-id: metaphysics
description: Hume's regularity account of causation, counterfactual theories, mechanistic theories, and causal pluralism.
language: en
---

# Causation

Causation is among the most pervasive features of reality and among the most philosophically contested. We invoke causal relations constantly: the window broke because it was struck by the ball; the fire spread because of the wind; the patient died because of the infection. Causal explanation, causal reasoning, and causal intervention underlie science, medicine, law, and everyday thought. Yet what causation *is* — what it is for one event to cause another — remains deeply controversial.

## Hume's Regularity Theory

Hume's analysis of causation, discussed in the context of empiricism (Chapter 4), remains the starting point for the contemporary debate. Hume distinguished two definitions of cause.

The first, in terms of *constant conjunction*: "An object, followed by another, and where all the objects similar to the first are followed by objects similar to the second" ^[Hume, D., *Enquiry*, §7.2]. Causation, on this view, is nothing over and above regular succession: whenever an event of type A occurs, an event of type B follows.

The second, in terms of *determination*: "An object followed by another, and whose appearance always conveys the thought to that other." This psychological definition reveals that the impression of necessary connection is in us, not in the objects.

The *regularity theory* developed from Hume's first definition. Mill systematised it with his *methods of agreement, difference*, and *concomitant variation* for identifying causal regularities ^[Mill, J.S., *A System of Logic*, 1843, III.viii].

**Objections:** Mere regular succession does not suffice for causation. Day regularly precedes night, but dawn does not cause dusk. Common causes produce correlated effects — thunder correlates with lightning, but neither causes the other. And regularities can be accidental (all gold spheres are smaller than the sun) rather than causal.

## Counterfactual Theories

David Lewis's *counterfactual theory* defines causation in terms of counterfactual dependence: C causes E if and only if, had C not occurred, E would not have occurred ^[Lewis, D., "Causation", *Journal of Philosophy* 70, 1973, pp.556-567].

This approach handles many cases better than regularity theories. The counterfactual "if the ball had not struck the window, the window would not have broken" is true (under normal conditions); hence the striking caused the breaking. Cases of accidental correlation are handled naturally: even if thunder and lightning are regularly correlated, it is not true that if thunder had not occurred, lightning would not have.

**Problems:** *Preemption* — where two potential causes compete and one "preempts" the other — is difficult. If two assassins shoot simultaneously and one bullet arrives first, the first shot caused the death; but it is not clear that the death counterfactually depends on the first shot, since the second would have caused it anyway. Lewis developed increasingly complex responses involving *fragility*, *quasi-dependence*, and *influence* ^[Lewis, D., "Causation as Influence", *Journal of Philosophy* 97, 2000].

*Overdetermination* — where two simultaneous causes each suffice for the effect — creates parallel problems.

## Mechanistic Theories

*Mechanistic* or *process* theories hold that causation consists in the transmission of energy, momentum, or causal influence through a spatiotemporally continuous process ^[Salmon, W., *Scientific Explanation and the Causal Structure of the World*, Princeton UP, 1984; Dowe, P., *Physical Causation*, Cambridge UP, 2000].

Wesley Salmon proposed that causal processes are distinguished from *pseudo-processes* (like shadows) by their ability to transmit a *mark* — an alteration made at one point that propagates forward. Phil Dowe replaced this with a conserved quantity account: a causal process is one that transmits a conserved quantity (energy, charge, momentum).

Mechanistic theories have the advantage of closely tracking scientific practice — physicists and biologists routinely explain by identifying mechanisms. But they face difficulties with causation by absence (the bridge collapsed *because* the engineers failed to inspect it), negative causation, and the causation of absences.

## Interventionist Theories

James Woodward developed an *interventionist* account, appealing to the notion of ideal intervention ^[Woodward, J., *Making Things Happen*, Oxford UP, 2003]. A variable X causes Y if there is a possible ideal intervention on X (one that changes X independently of other causes of Y) that changes Y.

This connects causation to the notion of manipulation or control, and is particularly well-suited to the social and biological sciences. It captures the idea that causal claims are action-guiding: to know that X causes Y is to know that intervening on X will change Y.

Interventionism faces the question of whether the interventionist account is circular — since interventions are themselves causal notions.

## Singular Causation and the Problem of Many Levels

A recurring question: is causation a relation between *types* of events (event-type A regularly precedes event-type B) or between *tokens* — particular, individual events (this striking caused this breaking)?

Token causation matters for law: we want to know whether *this* person's negligence caused *this* accident, not whether negligence-type events generally precede accidents.

The *problem of causal exclusion* (closely connected to philosophy of mind) asks how mental causation is possible if everything is determined at the physical level. If the physical causes of my action fully determine it, what work is left for my mental states to do? ^[Kim, J., *Mind in a Physical World*, MIT Press, 1998]. This challenges non-reductive physicalism about mind.

**Causal pluralism** holds that there is no single analysis of causation that captures all uses of causal vocabulary ^[Hall, N., "Two Concepts of Causation", in *Causation and Counterfactuals*, ed. Collins et al., MIT Press, 2004]. There may be one concept of causation for physics, another for biology, another for the law. Pluralism is comfortable with this; the search for a unified account may be misconceived.

The contemporary causation debate is technically sophisticated and connects to philosophy of science, philosophy of mind, and action theory. What is clear is that Hume was right about one thing: the concept of causation is not simply read off the surface of experience but requires serious philosophical analysis.
