This is a proposal to investigate comprehension, the processes by which people understand what a speaker meant. The proposal places special emphasis on those processes that are inferential, that take account of immediate context, tacit agreements between the speaker and listeners about the use of language, and general knowledge about objects, events, and states in the world. The proposal is to investigate four fairly distinct phenomena that at present are poorly understood: innovations, juxtapositions, given and new information, and spatial metaphors. Innovations are expressions that people readily understand but have never heard before, as in "Bartoky music," "crow black hair," and "to Houdini one's way out of the locked closet." By what process do people come to the intended interpretation of these expressions? Juxtapositions are pairs of adjacent sentences that bear a particular relation to each other. How do people determine the relation the speaker intended. Given and new information denote, respectively, that part of a sentence that refers to previous knowledge and that part that imparts novel information. By what process do listeners infer what the given information refers to and what further assumptions they were meant to draw in order to identify that referent? Spatial metaphors are extentions of spatial terms to non-spatial dimensions, as in "high and low status." By what principles are these extensions made? How do listeners correctly understand novel metaphors of this type?