A symbol is a representamen which refers only to such objects and in such respects as it might determine an interpretant to refer to those objects in those respects, and is hereby alone essentially a representamen, not in virtue of a physical relation or of an agreement of characters, but by a relation subsisting only by virtue of a representation. There must, therefore, be some general rule which connects the symbol with its objects; and it represents whatever that general rule determines it to represent.