The aim of this article is to briefly discuss several motifs connected with language in Rousseau’s writing about upbringing. The most important of these are Rousseau’s insights into language acquisition which, in many ways, correspond with the discoveries of contemporary psycho-linguistics. We shall also consider the principle of linguistic parsimony as a basic rule of upbringing. This rule has serious consequences not for all areas of upbringing but also for Rousseau’s conception of the relation between the human mind and ideas. After examining several concrete examples which Rousseau uses to demonstrate the necessity of this rule, we point to one basic exception to this general principle – this is the function of language in the curbing of sexual fantasies in the maturing human being.