The present invention interprets natural language input using common sense reasoning. The invention avoids the combinatorial explosion that has occurred in other natural language understanding systems. The invention uses modules for parsing, disambiguation, formal semantics, anaphora resolution, and coherence, and a naive semantic lexicon. The naive semantic lexicon is consulted by the parsing, disambiguation, formal semantics, anaphora resolution, and coherence modules to determine whether an interpretation alternative is plausible based on the world knowledge contained in the naive semantic lexicon. The parsing module employs both a top-down and bottom-up parsing strategy. The parsing module consults the naive semantic lexicon to build a structure from natural language input that has both semantic and pragmatic plausibility. The invention uses a psychologically-motivated naive semantic ontology that provides a means for classifying concepts. The lexicon relates word senses to the ontological concepts, contains word sense-specific common sense knowledge, and connects syntactic information with the meaning of each word sense. Using the natural language understanding of the present invention, a process is used for retrieving text that includes the steps of: 1) natural language understanding of a document base, 2) natural language understanding of a text retrieval request (i.e., query), 3) a comparison of the output of steps 1 and 2.