We have grammars in our heads. That's why we can produce and understand unlimited numbers of sentences; why language can interact with other things inside our heads, like memory and vision and moral judgment; why people who suffer damage to their heads often lose their language in whole or in part; why PET scans show increased blood flow in particular bits of our brains when we carry out linguistic tasks under experimental conditions. The list is almost endless. But are the grammars (or I-languages) in our respective heads “psychologically real” as well as neurophysiologically real? The question has seemed unnecessarily vexed and has attracted amass of largely unfruitful debate. Why should there be a problem? Most people, including psychologists and philosophers, are happy with the idea that we have something in our heads which accounts for these phenomena. What they balk at is the complexity and opacity of the linguist's account of what we have in our heads. It is unexceptionable to suggest that we have a rule specifying that verbs precede their objects in English, because we can see immediately what the effect of contradicting that rule is: silly sentences like John onions eats instead of the correct John eats onions. It is not so obvious that the correct analysis of John was too clever to catch should contain three empty categories of the kind we saw in the previous chapter.