As a field, artificial intelligence has always been on the border of respectability, and therefore on the border of crack-pottery. Many critics have urged that we are over the border. We have been very defensive toward this charge, drawing ourselves up with dignity when it is made and folding the cloak of Science about us. On the other hand, in private we have been justifiably proud of our willingness to explore weird ideas, because pursuing them is the only way to make progress.