Nothing I've stated concerning feedback is hot air. Everything I've stated is mere mathematical definition or results from mathematical theory such as 1/0 is undefined and such. So what are you talking about? What exactly in control theory is arrived from assumption? Are you comparing General Relativity which inherently assumes postulates to Control Theory which is a result of mathematical application? What are the postulates involved in Control Theory - what assumptions are made to arrive at the results? You clearly do not know what a pole is. Here is a crash course on zeros and poles. Zeros are in the numerator and can be found by setting the numerator equal to ZERO. The reason they are called 'zeros' is because they are solutions to which function will be... guess... yes, ZERO. Now a pole is when the denominator is... take a guess, ahh yes, ZERO. Note that when the denominator is zero that the function is not zero, but undefined. These are called "poles". So yes, setting (1-GainxFeedback) = 0 will give GainxFeedback=1, i.e. a postive pole at 1. Are you sure you understand what a pole is yet?