This paper provides an analysis of articles in two unrelated languages: St'át'imcets (Lillooet Salish) and English child language. The article systems in these two languages display striking parallels, diverging in similar ways from that of English adult language. Our analysis involves a parametric difference between English and St'át'imcets. While in English adult language, article distinctions rely on the state of the common ground between speaker and hearer, in St'át'imcets they rely on speaker beliefs. Despite the similarities between the patterns of article use in St'át'imcets and child English, we propose that English-acquiring children set the parameter correctly for the English value very early, but that they initially lack a pragmatic concept requiring them to distinguish systematically between their own beliefs and the belief state of their interlocutor. This neutralizes the distinction between the two parameter values, causing the article system of English-speaking children to optionally resemble that of St'át'imcets adults. In terms of language acquisition theory, our study supports a revised version of the Strong Continuity Hypothesis, according to which children obey all principles of Universal Grammar and set parameters as soon as the relevant input is available. Any structures deviating from target language structures result from an immature pragmatic system.