This question occurred to me in this thread - http://www.usmessageboard.com/religion-and-ethics/68247-the-truth-about-judaism.html - but I didn't want to throw it off topic. I've been given several good reasons why Judaism doesn't proselytise. Fisty in that thread made the point that it wasn't the Abrahamic nature of Judaism (which it shares with Christianity and Islam) which has anything to do one way or the other with proselytising. But Christianity and Islam have proselytising as major parts of their doctrines. Why is that?