 Just as Peirce thought signs could be classified according to whether their sign-vehicles function in virtue of qualities, existential facts, or conventions and laws, he thought signs were similarly classifiable according to how their object functioned in signification. Recall that, for Peirce, objects “determine” their signs. That is to say, the nature of the object constrains the nature of the sign in terms of what successful signification requires. Again, Peirce thought the nature of these constraints fell into three broad classes: qualitative, existential or physical, and conventional and law-like. Further, if the constraints of successful signification require that the sign reflect qualitative features of the object, then the sign is an icon. If the constraints of successful signification require that the sign utilize some existential or physical connection between it and its object, then the sign is an index. And finally, if successful signification of the object requires that the sign utilize some convention, habit, or social rule or law that connects it with its object, then the sign is a symbol.