Design principles
Methods in the absence of principles are useless. Design principles serve as a foundation for making design decisions that reflect a set of values. They are a key part of what sets a Design system apart from a mere style guide.
Design principles are often referred to as heuristics (General usability heuristics).
As to the method there may be a million and then some, but principles are few. The man who grasps principles can successfully select his own methods. The man who tries methods, ignoring principles, is sure to have trouble. —Harrington Emerson
Reference
Jakob Nielsen. “10 Heuristics for User Interface Design: Article by Jakob Nielsen.” Nielsen Norman Group, 24 Apr. 1994, www.nngroup.com/articles/ten-usability-heuristics/. Accessed 1 Mar. 2021.
Harrington Emerson. 1912. The Twelve Principles of Efficiency. New York: The Engineering Magazine.
Wiff Rudd. 2020. Side by Side. Woodway, TX: WR Enterprises, 51.