| Summary: | This dissertation proposes a principle of "economy of command", arguing that it provides a simple and natural explanation for some well-known properties of human language syntax. The focus is on the abstract combinatorial system that constructs the hierarchical structure of linguistic expressions, with long-distance dependencies determined by the structural relation of c-command. Adopting the assumption of much recent work that properties of syntax reflect very general organizational principles, I propose that syntactic forms with fewer and shorter c-command relations are preferred. Within the boundaries of strict binary branching assumed here, this results in a preference for hierarchical tree structures to be shallow and bushy, rather than deep and narrow. I pursue two broad applications of this principle, to syntactic movement and phrase structure. I argue that movement, the displacement of material to thematically unrelated positions, is a mechanism to reduce the number and length of c-command relations in the affected structures. I detail the properties we expect if movement is driven by this principle, including antilocality, a size threshold effect, a class of island effects, and feedback effects on iterated patterns of movement. I argue that these predictions align well with recent empirical descriptions of syntactic movement. I develop an account in these terms of the cross-linguistic ordering of elements within nominal phrases. Utilizing a computer program, I show that a single underlying structure common to all languages can give rise to all and only the attested word order possibilities via c-command-reducing movements, and describe the required shape of this underlying structure. The principle of economy of command also makes predictions about the format of phrase structure. Among the possible ways to build self-similar syntactic structure, the phrasal forms that build trees with the fewest c-command relations are "endocentric", in the geometric sense that each phrase contains a unique local terminal, and every daughter of the phrase that does not contain its associated terminal is another phrase. This provides a structural basis for the mysterious headedness of phrases. These successes support the validity of the principle, and reinforce the broader project of seeking naturalistic explanation of linguistic properties.
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