What is Principle?

Alternative Forms: Principles
Legal Definition
A principle is a law or rule that has to be, or usually is to be followed, or can be desirably followed, or is an inevitable consequence of something, such as the laws observed in nature or the way that a system is constructed. The principles of such a system are understood by its users as the essential characteristics of the system, or reflecting system's designed purpose, and the effective operation or use of which would be impossible if any one of the principles was to be ignored.

Examples of principles are descriptive comprehensive and fundamental law, doctrine, or assumption, the normative rule or code of conduct, and the law or fact of nature underlying the working of an artificial device.
-- Wikipedia
Legal Definition
By this term is understood truths or propositions so clear that they cannot be proved nor contradicted, unless by propositions which are still clearer. They are of two kinds, one when the principle is universal, and these are kuown as axioms or maxims; as, no one can transmit rights which he has not; the accessory follows the principal, &c. The other class are simply called first principles. These principles have known marks by which they may always be recognized. These are, 1. That they are so clear that they cannot be proved by anterior and more manifest truths. 2, That they are almost universally received. 3. That they are so strongly impressed on our minds that we conform ourselves to them, whatever may be our avowed opinions.

2. First principles have their source in the sentiment of our own existence, and that which is in the nature of things. A principle of law is a rule or axiom which is founded in the nature of the subject, and it exists before it is expressed in the form of a rule. Domat, Lois Civiles, liv. prel. t. 1, s. 2 Toull. tit. prel. n. 17. The right to defend one's self, continues as long as an unjust attack, was a principle before it was ever decides by a court, so that a court does Dot establish but recognize principles of law.

3. In physics, by principle is understood that which constitutes the essence of a body, or its constituent parts. 8 T. R. 107. See 2 H. Bl. 478. Taken in this sense, a principle cannot be patented; but when by the principle of a machine is meant the modus operandi, the peculiar device or manner of producing any given effect, the application of the principle may be patented. 1 Mason, 470; 1 Gallis, 478; Fessend. on Pat. 130; Phil. on Pat. 95, 101; Perpigna, Manuel des Inventeurs, &c., c. 2, s. 1.
-- Bouviers Law Dictionary
Legal Definition
In patent law, the principle of a machine is the particular means of producing a given resultby a mechanical contrivance, Parker v. Stiles, 5 McLean, 44, 63, Fed. Cas. No. 10,749. The .principle of a machine means the modus operandi, or that which applies, modifies, or combines mechanical powers to produce a certain result; and, so far, a principle, if new in its application to a useful purpose, may be patentable. See Barrett v. Hall, 1 Mason, 470, Fed. Can. No. 1,047.
-- Black's Law Dictionary
Legal Definition
Fundamental truths or doctrines of law; comprehensive rules or doctrines which furnish a basis or origin for others; settled rules of action, procedure or legal determination.
-- Black's Law Dictionary
Legal Definition
A fundamental truth; an original cause; a motive. See 22 Fed. Cas. (U. S.) 207.
-- Ballentine's Law Dictionary