This article aims to give an overview of Carnap’s 1928 book Logical Structure of the World or Aufbau and the most influential interpretations of its significance. After giving an outline of the book in Section 2, I turn to the first sustained interpretations of the book offered by Goodman and Quine in Section 3. Section 4 explains how this empirical reductionist interpretation was largely displaced by its main competitor. This is the line of interpretation offered by Friedman and Richardson which focuses on issues of objectivity. In Section 5, I turn to two more recent interpretations that can be thought of as emphasizing Carnap’s concern with rational reconstruction. Finally, the article concludes by noting some current work by Leitgeb that aims to develop and update some aspects of the Aufbau project for contemporary epistemology.