We know that the earth is flat, but that knowledge isn't unimpeachable. Over the last 150 years we've constantly welcomed RE'ers to try andto contradict that knowledge.
If RE'ers are not able to contradict it, then FET can be said to be "beyond the power of contradiction," and meet the burden Samuel Birley Rowbotham outlined.
There is no such thing as absolute knowledge. "Beyond the power of contradiction" and "absolute knowledge" are not one in the same. "Beyond the power of contradition" simply means that our opponents are unable to contradict it.
Let's stop over at Webster's first:
to be aware of the truth or factuality of : be convinced or certain of
Well it seems that you've modified the definition, as you 'know' but are no longer certain of. So when an FEer says that he/she 'knows' something, I guess that means just that he/she are 'pretty sure' only.
Next, let's turn to Parallax:
Let the method of simple inquiry--the "Zetetic" process be exclusively adopted--experiments tried and facts collected--not such only as corroborate an already existing state of mind, but of every kind and form bearing on the subject, before a conclusion is drawn, or a conviction affirmed.
Okay, then you indeed have left the Zetetic Method behind. I guess that it wasn't working out for you.
Finally, let's visit Parallax on whether he concluded the Earth flat:
If, to ascertain the true figure and condition of the earth, we adopt the "Zetetic" process, which truly is the only one sufficiently reliable, we shall find that instead of its being a globe--one of an infinite number of worlds moving on axes and in an orbit round the sun, it is the directly contrary--a Plane, without diurnal or progressive motion, and unaccompanied by anything in the firmament analogous to itself; or, in other words, that it is the only known material world.
Robotham concludes that the Earth is flat and published that conclusion in 1881. I have to wonder the reason you disagree with him now. Is the Zetetic Method faulty and was Robotham wrong?