Mill's Methods

We study causal relationships by trying to identify the factors that are necessary and/or sufficient for the effect we want to explain. This is what's wrong with the post hoc fallacy: the assumption that because A preceded B, A must have caused B. The fact that A came first is certainly relevant, but all by itself it gives us no reason to think that A was either necessary or sufficient for B.

What sort of evidence, then, can we use? The nineteenth-century philosopher John Stuart Mill formulated several methods for establishing evidence of a causal connection. They are known as:

Despite their formidable names, Mill's methods are used in everyday, common-sense reasoning about causality; they are also used by scientists in designing experiments.


Comprehension Questions

1 Identify which of Mill's methods is used to support the conclusion.

Part of the damage to the aircraft could be attributed to its impact with the ground. Another part was definitely due to the wind shear that the plane experienced as it fell from the sky. However, some of the damage cannot be accounted for by either of these factors. Investigators are examining this evidence closely for evidence of explosives.

a) Method of Agreement
b) Method of Difference
c) Method of Concomitant Variation
d) Method of Residue
2 Identify which of Mill's methods is used to support the conclusion.

No college wrestler has died in fifteen years until now. Why did Rocky die? He was using creatine.

a) Method of Agreement
b) Method of Difference
c) Method of Concomitant Variation
d) Method of Residue
3 Identify which of Mill's methods is used to support the conclusion.

Charles worked for two years at a hospital. During this time, the number of deaths increased dramatically.

a) Method of Agreement
b) Method of Difference
c) Method of Concomitant Variation
d) Method of Residue
4 Identify which of Mill's methods is used to support the conclusion.

At first we could not determine the cause, but then we noticed that there were more cases of the infection when more monkeys from Uganda were present.

a) Method of Agreement
b) Method of Difference
c) Method of Concomitant Variation
d) Method of Residue


Return to Tutorial Index

© Copyright 1998, W.W. Norton & Co.