Actually, the thing I thought about was the mathematical concept of the "infinitesimal". This is an idea that there is an infinitely small but non-zero unit underlying all mathematics. I don't understand it, but it seems that 1 + 1+ an infinitesimal = a number that is still 2, even though you have added a term to the old 1 + 1 = 2. So as I said, even the most fundamental truths of mathematics are always being questioned. Still, it is only in very special situations that 1+1=2 doesn't work.
And of course it's clear that the indefinability of pi, the Golden Ration and "e" are exactly what gives them explanatory value - somehow. They are not numbers but eternally undefined relationships. But who, other than religionists and scientists, is satisfied with the idea of undefinability?
Again, science is completely at ease with the unknown and the undefinable.
And it's not that things which can't be demonstrated scientifically don't exist. It's that we can't explain them. The answer is "I don't know" and science is mure beyond that. Science does not suggest that the world we cannot see doesn't exist. Science is based on the idea that Nature is as it is and we will always look at it through a cracked and clouded lens.
Engineering, on the other hand, is filled with prejudices.
Boddi