From the late 1930s to the mid 1960s Logical Empiricism dominated how North American scientists and intellectuals understood scientific reasoning. At its core, Logical Empiricism opposed metaphysical philosophies, favoring in their place reasoning grounded in analytic truths (that is, statements that are true or false because of the meaning and arrangement of their terms, not because of the state of the natural world to which they refer). From this analytic foundation arose a unity of sciences, united by common fundamental principles. This conference will examine the historical, philosophic, social and political factors that gave rise to Logical Empiricism in North America. It will develop a deeper understanding of how the ideas and people associated with those ideas came to North America and became established. The conference will take place at Harvard University, Cambridge, Massachusetts, in May 1998, and an edited volume of conference papers will be published.