According to Aristotle, both urban planning and political philosophy originated in the work of one man, Hippodamus of Miletus. If Aristotle is right, then the study of Hippodamus's work should help us understand their history as interrelated fields. Unfortunately, it is difficult to determine with any degree of precision exactly what Hippodamus's contributions were to these two fields when the two fields are studied separately. In urban planning, Hippodamus was traditionally credited with having invented the ''grid pattern'' in which straight (...) streets intersect each other at right angles to form regular city blocks. However, as grid patterned cities have been discovered that were built before Hippodamus's birth, this traditional attribution must be false. In political philosophy, Hippodamus was credited with having written the first utopian ''constitution''. However, Aristotle's account of this constitution is so brief that it is difficult to determine what philosophical position lies behind it and, as that account makes clear, several of the laws governing Hippodamus's ideal city seem contradictory. In this paper, I argue that Hippodamus did significant work in both fields but that his intentions can only be seen clearly if his philosophical and architectural works are read together. This reading not only makes clear the unique contribution that Hippodamus made to both disciplines, but it shows how they were-and perhaps how they should be-related. (shrink)