George Bernard Shaw said in Man and Superman that:
He who can, does. He who cannot, teaches.
While this quote is somewhat amusing, I'll make the claim here that it is false, and that it should no longer be taken for granted, as a way to undervalue all the great teachers out there (of all kinds).
It's not true that those who can't do, teach (some of the best hackers I know are professors), but it is true that there are a lot of things that those who teach can't do.
However, I found earlier insights to that in the so-called Jewish "Oral Torah", where various Jewish scholars, in many periods, collaborated and ended up saying that "I learned a lot from my teachers, and from my peers more than from my teachers, and from my students the most". (There's an old page about it in Visual Hebrew on the Hertzog College site.) That was during the middle ages, many centuries before Shaw (though it is possible there were older, similar, insights among Greek or Roman philosophers).
I think it means that one learns more by experiencing than by passive learning, and even more than that by teaching. From my experience in working on the "Perl for Perl Newbies" series of tutorials (and further educational material about software-related topics down the road), I can say that I had to structure my thoughts in a logical and deductive way, that my intended audience will be able to understand after reading it in order (or maybe only after skimming parts of it). I'm not sure if I did a very good job, but it still increased my understanding of Perl higher than the many years I've actively written Perl code. A different software trainer I talked with claimed that he invests about 24 hours in preparing the material for every hour of training he is giving. I've also gotten many similar insights from educating people with their Perl problems on various on-line forums.
So, we should realise that those who teach well, can. There are a lot of bad teachers of all sorts out there, but being a good teacher requires that you have a good understanding of the material, be high competent, and also work very hard (which despite popular belief, can still bring a lot of joy and happiness). It's high time we put the "Those who can, do; those who can't teach" prejudice to rest.
(Also see what I've written about the variation "Those who can, do; those who can't, complain.".)
This work is licensed under the Creative Commons Attribution 3.0 License (Unported) (CC-by) or at your option any later version. Copyright © 2011, Shlomi Fish. CC-by is a common, permissive, free/libre/open licence for cultural works, which allows for almost unlimited use. See my interpretation and expectations from people who wish to build upon it (which I believe are pretty fair).
This was a small filler post for this blog ( "Unarmed but still Dangerous" ), as I'm busy working on some other articles and essays, and enhancing some existing essays and stories. I had previously written about it in my essay "Thoughts about the Best Introductory Language", but I think it got lost in confusion, and did not make a large enough impact on the Blogosophere there.
My previous post proved to be very popular after it was Slashdotted successfully, and afterwards featured on some other news sites, blogs, microblogs, and on-line forums (some people told me it became "viral"). So I'm happy with all the attention, and that "Unarmed but still Dangerous", has gotten off on the right foot.
Moreover, my introductory post was covered in Eric Raymond's "Armed and Dangerous" blog (after I refered him to the fact that my blog's name was a parody and tribute to his) and sparked an active discussion there. The blog appears to be down at the moment, but I'll give a link to the discussion once it is up again. Update: Here is the post with the discussion.