>>13996680Clean and dirty have social or scientific definitions depending on context.
When I pressure wash my driveway, it is "clean" when it looks like the dark grey has been washed away and appears nicest outside my house. When I am cleaning something in the lab, if high precision and exacting standards are needed, we set a somewhat arbitrary cutoff (some threshold below which the effects of material residue are negligible). Once it is below this threshold, it is "clean."
As real as science seems, it is only objectively correct within the terms and definitions we create and find to be useful. Reality or truth or whatnot could/does exist outside of the terms or definitions we describe, so science cannot be the same thing as complete truth. That hardly changes its usefulness, so if clean and dirty are useful ideas, we use them.