A and B occur together.
A occurs before B.
Changing A changes B.
A is a better explanation of B than other possible causes.
Therefore, A causes B.
Examples: sex causes pregnancy, HIV causes AIDS.
A and B tend to occur together.
Not-A and not-B tend to occur together.
A and not-B do not tend to occur together.
Not-A and B do not tend to occur together.
Therefore, A and B are positively correlated.
Consider all four cells:
| B | Not B | |
| A | don't just focus on this cell | look for counterexamples |
| Not A |
The competing hypotheses are H1, H2 ...
The available evidence is E1, E2, ...
Hypothesis H1 is a better explanation of the evidence than the other hypotheses, because:
Therefore, we are justified in believing H1.
1. What is the claim?
2. Who is making the claim?
3. What is the evidence?
4. What is the best explanation of the evidence?
Updated Jan. 27,, 2003