A mathematician, physicist, and engineer are taking a math test. One question asks "Are all odd numbers prime?"
The mathematician thinks, "3 is prime, 5 is prime, 7 is prime, 9 is not prime -- nope, not all odd numbers are prime."
The physicist thinks, " 3 is prime, 5 is prime, 7 is prime, 9 is not prime -- that could be experimental error -- 11 is prime, 13 is prime, yes, they're all prime."
The engineer thinks, " 3 is prime, 5 is prime, 7 is prime, 9 is prime, 11 is prime, ..."