A set of six conditions for critically analyzing proposals in the various areas of language acquisition is developed and justified. These conditions are then applied to theoretical proposals in language acquisition literature. Proposals in the following areas are discussed and evaluated: (1) phonological development, (2) early lexical development, (3) the acquisition of relational terms, (4) the development of formal grammars, (5) semantic approaches to syntactic development, (6) the development of speech acts, (7) cognitive reductions, and (8) social reductions. Theories on learnability and the mechanisms of learning are also discussed. Recommendations for future language acquisition research are included. (EKN)