>Mike: fuzzy logic doesn't "know" anything; it would be more useful to
>the debate to limit that sort of personification.

I think I implied that in the second half of the paragraph.

>For that matter, the closed form math doesn't "know" where the poles
>& zeros are, either, no matter what algorithm you choose to
>express it.

Your right, the engineer who analyzed the plant response knows
where the poles and zeros are, and his closed form algorithm
provides the gain and phase compensation.

>And, most importantly, physical processes don't have poles & zeros,
>anyway. The poles & zeros are a feature of your mathematical model of
>the process.

I don't know where you studied control theory, but If you are using
a linear time-invariant system to control a physical process, It
had better have a response in the frequency domain.

>There is no reason that I know of to believe that there
>are no other valid models of physical processes, or to
>believe that other models might not be as good.

I didn't say there were no other valid models.  I said if you have
a model which in closed form, you know what compensation will
provide stability for all time.

                                Regards,
                                   Mike