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Causal Reasoning
One common way to explain a phenomenon is to cite its cause. You can understand
why your clothes shrunk by learning what caused them to shrink. Was the water
too hot when you washed them, did you dry them too long, or was it some combina-
tion of factors? In order to determine what causes what, we need to engage in a new
kind of inductive reasoning—causal reasoning—which is the topic of this chap-
ter. Causal reasoning is often based on negative and positive tests for necessary
conditions and for sufficient conditions. After developing these tests and applying
them to a concrete example, we will discuss concomitant variation as a method of
drawing causal conclusions from imperfect correlations. Our goal throughout this
chapter is to improve our ability to identify causes so that we can better understand
why certain effects happened and also make better predictions about whether similar
events will happen in the future.Reasoning About Causes
If our car goes dead in the middle of rush-hour traffic just after its 20,000-mile
checkup, we assume that there must be some reason why this happened.
Cars just don’t stop for no reason at all. So we ask, “What caused our car to
stop?” The answer might be that it ran out of gas. If we find, in fact, that it
did run out of gas, then that will usually be the end of the matter. We will
think that we have discovered why this particular car stopped running. This
reasoning is about a particular car on a particular occasion, but it rests on
certain generalizations: We are confident that our car stopped running when
it ran out of gas, because we believe that all cars stop running when they run
out of gas. We probably did not think about this, but our causal reasoning in
this particular case appealed to a commonly accepted causal generalization:
Lack of fuel causes cars to stop running. Many explanations depend on
causal generalizations.
Causal generalizations are also used to predict the consequences of par-
ticular actions or events. A race car driver might wonder, for example, what
would happen if he added just a bit of nitroglycerin to his fuel mixture.
Would it give him better acceleration, blow him up, do very little, or what?97364_ch10_ptg01_215-238.indd 215 15/11/13 10:48 AM
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