Systematicity is the thesis that there are predictable patterns among which thoughts a thinker is capable of entertaining. Thinkers that can entertain thoughts of certain structures can always entertain distinct thoughts that have related structure. For instance, any thinker who can think a complex thought of the form “X transitive verb Y” can think “Y transitive verb X”.[31] Systematicity entails that we won’t find any thinker that can only think one of those two thoughts, in which case we could not find a person who could think audrey wronged max, but not   max wronged audrey. Of course, these two thoughts have very different effects in one’s cognitive economy. The challenge for the associationist is to explain how the associative structure  audrey/wronged/max can be distinguished from the structure  max/wronged/audrey, while capturing the differences in those thoughts’ effects.