It occurs to me that you can never evaluate your own teaching ability, absent feedback. It is the students who judge the teachers capacity. It is not what you know, but what you can communicate that matters, which necessarily means that only on the highest levels is there a strong correllation between knowledge and teaching ability, and even there one can only speak of capacity–potential–and not product.
An interesting corrollary to this is that if we look at Lao Tzu’s aphorism, “A good man is the teacher of a bad man, and a bad man a good man’s charge” (close), then if you cannot meaningfully communicate goodness, you are not a good person. By this, I mean the capability of altering peoples behavior in observable ways. The classic example of NOT teaching is to say one thing and do another.
By this measure, I think it is a necessary conclusion that in many important respects, Mohammad was not a good man. Among other things, he advocated the physical slaughter of all non-Muslims–which will not be found in the New Testament, and only where the land of Israel is concerned in the Old–and married a six year old, consummating the marriage when she was nine.
This story speaks volumes about the cultural development within Islam:
http://www.theblaze.com/stories/saudi-cleric-issues-fatwa-defending-pedophilia-as-%e2%80%98marriage%e2%80%99/
Why is pedophilia wrong? Within my terms, because it necessarily invokes a power relationship. The practice of marrying children is nothing but an extension of the more general rejection of the rights of women, which, again, invoke a power relationship. Anyone whose sense of self depends upon the subjugation of others is a bad person, and if they actively enjoy that subjugation–which is implied by marrying and raping 9 year olds–then they are evil.