What is 2*2?

Several scientists were all posed the following question: "What is 2 * 2 ?"  

• The engineer whips out his slide rule (so it's old) and shuffles it back and forth, and finally announces "3.99".
• The physicist consults his technical references, sets up the problem on his computer, and announces "it lies between 3.98 and 4.02".
• The mathematician cogitates for a while, then announces: "I don't know what the answer is, but I can tell you, an answer exists!".
• Philosopher smiles: "But what do you mean by 2 * 2 ?"
• Logician replies: "Please define 2 * 2 more precisely."
• The sociologist: "I don't know, but is was nice talking about it".
• Behavioral Ecologist: "A polygamous mating system".
• Medical Student : "4" 
• All others looking astonished : "How did you know ??" Medical Student : :I memorized it."