Doug Miller wrote:

I never contended otherwise. You, on the other hand, contended that
knowledge
of the subject was the only necessary attribute to be able to teach.

Let's do a thought experiment. For the purposes of the experiment,
we will stipulate that you have expert knowledge of chemistry, and
that you speak, understand, read, and write only Polish, and no
other language. Your assignment is to teach high school chemistry
in Birmingham, Alabama.

How helpful is that expert knowledge of chemistry in teaching a
classroom full of students who can't understand anything you say?

Reverse it.

So you think that you'd be able to teach that class -- after all, you
have
expert knowledge of the subject, and (according to you) that's all
that's
necessary.

Consider the "teaching experience" of a retired, Ph.D. chemical engineer,
who, by law, is deemed incompetent to teach in the public schools.

He's got 20 years experience as a student in a classroom. As a grad student,
he most likely has at least four years experience teaching undergraduate
students in basic college chemistry, organic chemistry, and quantitative
analysis.

As head of a commercial lab for, say, ten years, he's had to keep up with
professional publications and teach the newer techniques to his
subordinates.

It is incredible to believe he can't muddle through high school chemistry
(or, for that matter physics, algebra, and other math courses).