An engineer, a physicist and a mathematician want to catch a lion. The engineer goes to Africa, builds a cage and traps the lion in it. The physicist builds a f

An engineer, a physicist and a mathematician want to catch a lion. The engineer goes to Africa, builds a cage and traps the lion in it. The physicist builds a fence around Africa and pronounces: "I've trapped the lion". The mathematician builds a cage, climbs inside and pronounces: "I am outside".