Many inductive arguments are about causes: this made that happen. They often start from a correlation, two things that tend to happen together.
Key idea
Two things happening together does not show that one causes the other. Before concluding "A causes B", check for a common cause, a reversed direction, and coincidence.
Why it works
A correlation fits several stories. Ice cream sales and sunburns rise together because sunny weather causes both. Towns with more firefighters have more fires because fires lead towns to hire firefighters, not the reverse. And with enough pairs of things, some will line up by chance. A cause claim needs evidence that rules these out, such as a fair test that changes one thing and holds the rest the same.
| Pattern | Other explanation | Kind |
|---|---|---|
| Ice cream sales and sunburns rise together | Hot, sunny weather causes both | Common cause |
| Towns with more firefighters have more fires | More fires lead to hiring more firefighters | Reversed direction |
| The team won the day Kai wore green socks | Socks can't change a game | Coincidence |
Worked example: Check the arrow
"People who visit the doctor more often are sick more often. So doctor visits make people sick."
- Is there a third thing causing both? Not an obvious one.
- Could the arrow point the other way? Yes: being sick is what sends people to the doctor.
Answer: Reversed direction.
Worked example: A fair test
Half of the bean plants, chosen at random, get fertilizer; the rest do not; everything else is kept the same. The fertilized ones grow taller. Is "the fertilizer helped" well supported?
- Random choice and equal care rule out a common cause.
- We changed the fertilizer first, so the direction is clear.
- A large, steady difference is unlikely to be chance.
Answer: Yes: this is good causal reasoning.
Common mistake
Reading correlation as causation. Before you accept "A causes B", ask: could something cause both? Could B cause A? Could it be chance?