Named after Protagoras - Greek philosopher (c. 485-415 B.C.).
Protagoras is a lunar impact crater on the Mare Frigoris in the northern part. To the north-northwest is the slightly larger crater Archytas, and to the southeast is the prominent Aristoteles. The rim is circular and rises above the surrounding flat terrain, although the rim dips down along the southwestern edge. The interior floor contains a few light markings but no formations of interest. (wikipedia entry)