"Principle" in the Context of Science

A principle in science is something which is not derived but is simply stated without proof.


  1. Heizenberg's Uncertainty Principle is not a principle being derived from other quantum mechanical ideas. It is increasingly referred to as "Heizenberg's Uncertainty Relations."
  2. The Principle of Microscopic Reversibility is, surprisingly perhaps, not believed to be a consequence of the Second Law of Thermodynamics and therefore constitutes a true principle.
  3. The Principle of Equivalence is a straightforward principle: It states that it is impossible to decide whether one is accelerating or rather is in a gravitational field. Einstein gave the example of being inside a chest, hanging in space from a rope. Some being pulls on the rope with a constant force. Quickly the chest reaches unheard of velocities. The person inside the chest, initially floating in zero gravity, "falls" to the floor. A hammer and a feather fall and hit the ground at the same time. Should the man climb out of the chest and see the rope pulling the chest upward he is at liberty to say, "That's why the chest is not falling - it is suspended from this rope."

Prin"ci*ple (?), n. [F. principe, L. principium beginning, foundation, fr. princeps, -cipis. See Prince.]


Beginning; commencement.


Doubting sad end of principle unsound. Spenser.


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.


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.


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.


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. Chem.

Any original inherent constituent which characterizes 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 under Bitter, Contradiction, etc.


© Webster 1913.

Prin"ci*ple (?), v. t. [imp. & p. p. Principled (?); p. pr. & vb. n. Principling (?).]

To equip with principles; to establish, or fix, in certain principles; to impress with any tenet, or rule of conduct, good or ill.

Governors should be well principled. L'Estrange.

Let an enthusiast be principled that he or his teacher is inspired. Locke.


© Webster 1913.

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