Like any other medium, it is a staple, a natural resource. 
As an outward and visible form of the urge to change and to 
exchange, it is a corporate image, depending on society for its 
institutional status. Apart from communal participation, 
money is meaningless, as Robinson Crusoe discovered when he 
found the coins in the wrecked ship:

          I smiled to myself at the sight of this money. “O 
     drug!” said I aloud, “What art thou good for? Thou art 
     not worth to me—no, not the taking off the ground: one 
     of those knives is worth all this heap: I have no manner of 
     use for thee; e’en remain where thou art and, go to the 
     bottom, as a creature whose life is not worth saving.”
          However, upon second thoughts, I took it away; and 
     wrapping it all in a piece of canvas, I began to think of 
     making another raft . . .