Homophones

• principal

Noun

Singular principle

Plural principles

principle (plural principles)

1. A fundamental assumption.

   We need some sort of principles to reason from.

2. A rule used to choose among solutions to a problem.

   The principle of least privilege holds that a process should only receive the permissions it needs.

3. (generally plural) Moral rule or aspect.

   I don't doubt your principles; you are clearly a person of principle.

   It's the principle of the thing; I won't do business with someone I can't trust.

4. (physics) A rule or law of nature, or the basic idea on how the laws of nature are applied.

   Bernoulli's principle

   The Pauli Exclusion Principle prevents two fermions from occupying the same state.

   The principle of the internal combustion engine

5. (somewhat dated) A fundamental essence, particularly one producing a given quality.

   Many believe that life is the result of some vital principle.

   Cathartine is the bitter, purgative principle of senna. — Gregory.

6. (obsolete) A beginning.

   Doubting sad end of principle unsound. — Spenser.

A principle is a comprehensive and fundamental law, doctrine, or assumption. It can be a rule or code of conduct. It can be a law or fact of nature underlying the working of an artificial device.

Principle as cause

The principle of any effect is the cause that produces it.

Depending on the way the cause is understood the principle as cause acquires nuances.

Principle of Causality, as efficient cause

The efficient cause is the one that produces the necessary effect, as long as the necessary and sufficient conditions are provided.

The scientific process generally consists of establishing a cause by observing the effects. Using the principle that same causes always produce the same effects, a law can be established for which causes produce which. In this way the principle of cause is considered as a determining factor in the production of the facts.

Each science establishes the type of principles or causes that determine their investigation, on which they establish their method.

With the belief that "every effect has a cause", it's considered that everything that exists must have a cause. This is considered as the principle of causality. It was formulated by Aristotle as "Everything that moves is moved by another". This principle has been frequently used as a demonstration of God's existence, along with the principle of sufficient reason.