In science, a principle is a general statement, unproved, but justified a posteriori by verification of its consequences. [1] In loose terms a principle is a theory that has solidified to a good amount. In the 19th centuries, the first law and second law were referred to as the first main principle and second main principle.

Quotes
The following are related quotes:

“Of those who hold that the first principle is one, moving, and infinite, Anaximander, son of Praxiades, a Milesian, who was a successor and pupil of Thales, said that the infinite is principle and element of the things that exist. He was the first to introduce this word ‘principle’ <??>. He says that it is neither water nor any other of the so-called elements but some different infinite nature, from which all the heavens and the worlds in them come into being.”
— Simplicius (c.550), Commentary on Aristotle’s Physics (24.13) (Ѻ)

See also
● Zeilinger’s principle
● Principle of inertia
● Maximum entropy principle
● Principle of the transmission of work
● Principle of elementary disorder
● Carnot’s principle
● Le Chatelier’s principle
● Principle of substance stability
● Landauer’s principle

References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics (principle, pg. 247-48). Oxford: Oxford University Press.

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