Battles over public space involve conflicts of values that express themselves in planning policies as well as the built environment. However, the dominant conceptions of public space in planning practice and the academic literature support a limited range of those values. I argue that conceptions based on openness and accessibility play into a particular construction of public life that emphasises casual interactions and downplays purposive, political ones. Following a conceptual analysis of the public-private distinction, the paper offers a novel, threefold account of public space; argues that democracy requires a particular kind of publicness not recognised by the commonly accepted definition; and deploys a simple content analysis to highlight the conceptual emphases and absences in planning policy in the political heart of London. I argue that some advocates of public space are unwittingly supporting restrictive planning and design practices that limit important kinds of democratic expression.