Terrorists sometimes blow themselves up. Does that make them irrational?

**Takeaway Points**

- In ordinary language, rational and sensible are synonyms.
- In modeling terms, an actor is rational if his preferences are
*complete*and*transitive*. - A complete preference means that for any two alternatives A and B, the actor prefers A to B, prefers B to A, or is indifferent. There is no “decline to state” option.
- A transitive preference means that for any three alternatives A, B, and C, if the actor prefers A to B and prefers B to C, then he must also prefer A to C. Preference cycles are not allowed.
- Rational preferences therefore may not be sensible. But we can model them all the same.