1. Beginning; commencement. Doubting sad end of principle unsound. (Spenser)
2. A source, or origin; that from which anything proceeds; fundamental substance or energy; primordial substance; ultimate element, or cause. The soul of man is an active principle. (Tillotson)
3. An original faculty or endowment. Nature in your principles hath set benignity (Chaucer) Those active principles whose direct and ultimate object is the communication either of enjoyment or suffering. (Stewart)
4. A fundamental truth; a comprehensive law or doctrine, from which others are derived, or on which others are founded; a general truth; an elementary proposition; a maxim; an axiom; a postulate. Therefore, leaving the principles of the doctrine of christ, let us go on unto perfection. (Heb. Vi. 1) A good principle, not rightly understood, may prove as hurtful as a bad. (milton)
5. A settled rule of action; a governing law of conduct; an opinion or belief which exercises a directing influence on the life and behavior; a rule (usually, a right rule) of conduct consistently directing one’s actions; as, a person of no principle. All kinds of dishonesty destroy our pretenses to an honest principle of mind. (Law)
6. (Science: chemistry) Any original inherent constituent which characterises a substance, or gives it its essential properties, and which can usually be separated by analysis; applied especially to drugs, plant extracts, etc. Cathartine is the bitter, purgative principle of senna. (Gregory) Bitter principle, Principle of contradiction, etc. See Bitter, Contradiction, etc.
Origin: F. Principe, L. Principium beginning, foundation, fr. Princeps, -cipis. See Prince.