- First principle
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**"First Principles**is also the title of a work byHerbert Spencer ."Inphilosophy , a**first principle**is a basic, foundational proposition or assumption that cannot be deduced from any other proposition or assumption. Inmathematics , first principles are referred to asaxiom s orpostulate s.**First principles in formal logic**In a formal

logical system , that is, a set ofpropositions that are consistent with one another, it is probable that some of the statements can be deduced from one another. For example, in thesyllogism , "All men are mortal; Socrates is a man; Socrates is mortal" the last claim can be deduced from the former two.A

**first principle**is one that cannot be deduced from any other. The classic example is that ofEuclid 's (seeEuclid's Elements ) geometry; its hundreds of propositions can be deduced from a set of definitions, postulates, and common notions: all three of which constitute "first principles."**Aristotle's contribution**Aristotle , author of the earliest surviving text on logic, formulated a principle (**the Aristotelian**denoted A=A ) that later achieved the historical distinction of being calledtautology **the first principle**as a proper name. It occurs in those of his writings that have come to be called theMetaphysics . The principle in Greek, and its transliteration, is ("Meta ta physica", 1005b)::"τὸ γὰρ αὐτὸ ἅμα ὑπάρχειν τε καὶ μὴ ὑπάρχειν ἀδύνατον τῷ αὐτῷ καὶ κατὰ τὸ αὐτό":"to gar auto hama hyparchein te kai me hyparchein adynaton to auto kai kata to auto."

and in English translation:

:"For the same (characteristic) simultaneously to belong and not belong to the same (object) in the same (way) is impossible."

This principle is the first expression of consistency in western thought. Any defining and reasoning in any language on any topic assumes it a priori. It cannot be doubted, as all doubting is based on inconsistency, which assumes consistency a priori.

Descartes Profoundly influenced by

Euclid , Descartes, the "father of modern philosophy", was arationalist who invented thefoundationalist system of philosophy. He used the "method of doubt", now calledCartesian doubt , to systematically doubt everything he could possibly doubt, until he was left with what he saw as purely indubitable truths. Using these self-evident propositions as his "axioms", or "foundations", he went on to deduce his entire body of knowledge from them. (The foundations are also called "a priori " truths.) His most famous proposition is "I think, therefore I am", or "Cogito ergo sum".John Duns Scotus "A Treatise On God As First Principle" is about the

First Cause , or the Prime Mover, that iseternal , and exists, prior to theorder of beings, and prior tocreation .**In physics**In

physics , a calculation is said to be "from first principles", orab initio , if it starts directly at the level of established laws of physics and does not make assumptions such as model andfitting parameters.For example, calculation of

electronic structure usingSchrödinger's equation within a set of approximations that do not include fitting the model to experimental data is an "ab initio" approach.**See also***

A priori

*Ab initio

*Axiom

*First Cause

*Fuzzy Logic

*Intuitionism

*Law of excluded middle

*Law of noncontradiction

*Metaphysics

* Prime Mover

*proposition **External links*** [

*http://aleph0.clarku.edu/~djoyce/java/elements/elements.html Euclid's Elements*]

* [*http://www.ewtn.com/library/THEOLOGY/GODASFIR.HTM A TREATISE ON GOD AS FIRST PRINCIPLE by John Duns Scotus*]

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