Donald Martin is chairman of the Physics, Astonomy, and Energy Science Department at the College of Marin in Kentfield, California. He received his A.B. from the University of California, Berkeley, and his M.A. from San Jose State University. He has long been interested in the problems that students have in developing their reasoning and critical thinking skills. Recently, this interest has led him to the LOGO computer language, a course he now teaches on a UNIX-based system at the college.