Just cause knowledge can be reduced to predictive capabilities and judgement calls does not mean systems are defined arbitrarily. Everything is defined as to its relative function in/to society and our material endeavors and the social forces that limit or expand on areas of these systems.
First we have to live. That has implications; it's the base for all knowledge.
Knowledge is developing all the time and can be uncertain, sure, but the foundations aren't arbitrary.
You are doing an idealism.