Two theories of movement have been proposed to capture properties of displacement in natural language – the trace theory and the copy theory. These theories differ in their assumptions regarding the lexical contentfulness of an object left behind by movement. Capitalizing on this difference, the present two‐part article scrutinizes predictions made by the two theories to investigate movement properties. In Part I of the article, exploring facts from reconstruction and ellipsis, we establish the generalization that A'‐movement obligatory leaves behind a copy of a moved element, but A‐movement only optionally does.