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.