Associative structures are most naturally contrasted with propositional structures. A pure associationist is opposed to propositional structures—strings of mental representations that express a proposition—because propositionally structured mental representations have structure over and above the mere associative bond between two concepts. Take, for example, the associative structure  green/toucan. This structure does not predicate green onto toucan. If we know that a mind has an associative bond between  green and  toucan, then we know that activating one of those concepts leads to the activation of the other. A pure associative theory rules out predication, for propositional structures aren’t just strings of associations. “Association” (in associative structures) just denotes a causal relation among mental representations, whereas predication (roughly) expresses a relation between things in the world (or intentional contents that specify external relations). Saying that someone has an associative thought  green/toucan tells you something about the causal and temporal sequences of the activation of concepts in one’s mind; saying that someone has the thought   there is a green toucan  tells you that a person is predicating greenness of a particular toucan (see Fodor 2003: 91–94, for an expansion of this point).