Consider which of the following sentences is sensible, and which is less so: 1a. After wading barefoot in the lake, Erik used his shirt to dry his feet. 1b. After wading barefoot in the lake, Erik used his glasses to dry his feet. Sentence 1a is sensible, whereas sentence 1b does not make much sense. But why? Both sentences are grammatical. Both meet obvious semantic constraints (e.g., shirts and glasses are inanimate). Both sentences generate coherent, integrated, well-formed propositions. Finally, the sentences do not differ in the associations among the terms. That is, both shirt and glasses are associatively unrelated to dry. The ability to discriminate between sentences such as these is taken as support for the Indexical Hypothesis. The hypothesis is based on three claims about how we understand words and sentences. First, words and phrases are indexed to objects in the world or to analogical representations of those objects such as pictures or perceptual symbols (Barsalou, under review). Second, we derive affordances from the objects. Third, and most importantly, the affordances, not the words, constrain the way ideas can be coherently combined or meshed.