This paper offers a functional explanation for the existence and for the special properties of movement rules in natural languages. A survey of reasonably well-established movement transformations in English reveals certain asymmetries in the classes of such rules encountered empirically and in their formal properties. It is argued that the special formal properties of backing rules correlate with their function, which is different from the function of raising, lowering, and fronting rules. The latter three types can be given a uniform functional characterization in terms of the notion ‘objective content’, a notion that has figured prominently, though implicitly, in the history of generative grammar. This notion is discussed in preliminary terms, as is that of relative ‘prominence’, whose syntactic relevance has been clearly established. The hypothesis is advanced that raising, lowering, and fronting rules all serve the function of increasing the prominence of objective content in surface structure. This hypothesis accounts for the asymmetries noted in regard to the movement rules of English, and it also provides a motivated explanation for the fact that backing rules are upward bounded. Movement rules are shown to be only one facet of a broad conspiracy to ensure the surface prominence of objective content. This conspiracy is further explored in the context of information theory and generative semantics.