All Odd Numbers are PrimeĀ
The mathematician says: "1 is prime, 3 is prime, 5 is prime, 7 is prime, therefore all odd numbers are prime."
The physicist says: "1 is prime, 3 is prime, 5 is prime, 7 is prime, 9 is ... observation error ..., 11 is prime, 13 is prime, therefore all odd numbers are prime."
The engineer says: "1 is prime, 3 is prime, 5 is prime, 7 is prime, 9 is prime, therefore all odd numbers are prime."