On what methodological differences does the historical division between hard and soft sciences generally hinge?

Answer

Degree to which variables can be isolated, controlled, and mathematically modeled

The fundamental distinction between hard and soft sciences is rooted in methodology, specifically how well researchers can isolate, control variables, and apply mathematical modeling to their subjects of study.

On what methodological differences does the historical division between hard and soft sciences generally hinge?
classificationastronomysciencehard science