This thesis introduces an experimental and quantitative approach to language through the study of the concept of soft constraints and its application to two phenomena of order in French: the position of the attributive adjective and the ordering of verbal complements occurring in postverbal position. Soft constraints are defined as affecting the acceptability rather than the grammaticality of the sentences. Our main hypothesis is that these constraints are properties of the language and thus must studied in syntax. These constraints raise a methodological issue: since they do not affect the grammaticality of the sentences, they cannot be investigated using the traditional tools of syntax (introspection and grammaticality judgment). It is th...