A discussion of the application of artificial intelligence to natural language processing looks at several problems in language comprehension, involving semantic ambiguity, anaphoric reference, and metonymy. Examples of these problems are cited, and the importance of the computational approach in analyzing them is explained. The approach applies specific mechanisms or models to natural language to make explicit the complex system of assumptions, knowledge, and processes used in understanding language. It is proposed that by examining language at the micro level it is possible to see how much a learner--whether a computer, a child, or a second language learner--must master. (MSE)