Over the last decade, many of the legal disputes that have arisen in the context of national security have concerned information—the withholding of it, the suppression of it, the collection of it, or the safeguarding of it. Frequently, these disputes have involved an argument known as the "mosaic" theory. The theory is straightforward: Seemingly insignificant information may become significant when combined with other information. Insofar as it states a fact about the world, the mosaic theory is uncontroversial. Usually, though, the mosaic theory is offered not as description but as argument. For example, it is offered as a justification for the government's withholding of information that would otherwise be released to the public, or for the government's silencing of citizens who would otherwise have a right to speak, or for the government's collection of information that citizens would otherwise keep confidential. When the mosaic theory is used in support of normative claims, the theory is controversial. I do not propose to resolve this controversy here, but by examining three distinct contexts in which the government has invoked the theory, we can gain insight into the theory's merits.