"Having some knowledge of the characteristics of the acquired grammars and the limitations on the available data, we can formulate quite reasonable and fairly strong empirical hypotheses regarding the internal structure of the language-acquisition device that constructs the postulated grammars from the given data. When we study this question in detail, we are, I believe, led to attribute to the device a very rich system of constraints on the form of a possible grammar; otherwise, it is impossible to explain how children come to construct grammars of the kind that seem empirically adequate under the given conditions of time and access to data. But if we assume, furthermore, that children are not genetically predisposed to learn one rather than another language, then the conclusions we reach regarding the language-acquisition device are conclusions regarding universal grammar."