Editing Principle (section)

==As axiom or logical fundament==
===Principle of sufficient reason===
{{Main|Principle of sufficient reason}}
The principle states that every event has a rational explanation.<ref>[https://plato.stanford.edu/entries/sufficient-reason/ "Principle of Sufficient Reason."] {{Webarchive|url=https://web.archive.org/web/20180611143503/https://plato.stanford.edu/entries/sufficient-reason/ |date=2018-06-11 }} ''Stanford Encyclopedia of Philosophy''. 7 September 2016. 25 October 2017.</ref> The principle has a variety of expressions, all of which are perhaps best summarized by the following:

:For every entity ''x'', if ''x'' exists, then there is a sufficient explanation for why ''x'' exists.
:For every event ''e'', if ''e'' occurs, then there is a sufficient explanation for why ''e'' occurs.
:For every proposition ''p'', if ''p'' is true, then there is a sufficient explanation for why ''p'' is true.

However, one realizes that in every sentence there is a direct relation between the predicate and the subject. To say that "the Earth is round", corresponds to a direct relation between the subject and the predicate.

===Principle of non-contradiction===
[[File:Aristoteles Louvre.jpg|thumb|upright|[[Bust (sculpture)|Portrait bust]] of Aristotle; an [[Roman Empire|Imperial Roman]] copy of a lost [[bronze sculpture]] made by [[Lysippos]]]]
{{Main|Law of noncontradiction}}
According to [[Aristotle]], "It is impossible for the same thing to belong and not to belong at the same time to the same thing and in the same respect."<ref>[https://plato.stanford.edu/entries/aristotle-noncontradiction/ "Aristotle on Non-contradiction."] {{Webarchive|url=https://web.archive.org/web/20180611021813/https://plato.stanford.edu/entries/aristotle-noncontradiction/ |date=2018-06-11 }} ''Stanford Encyclopedia of Philosophy''. 12 June 2015. 25 October 2017.</ref> For example, it is not possible that in exactly the same moment and place, it rains and does not rain.<ref>[https://oregonstate.edu/instruct/phl201/modules/Philosophers/Aristotle/aristotle_laws_of_thought.html "Great Philosophers."] ''Oregon State University''. 2002. 25 October 2017.</ref>

===Principle of excluded middle===
{{Main|Law of excluded middle}}
The principle of the excluding third or "principium tertium exclusum" is a principle of the traditional logic formulated canonically by [[Gottfried Wilhelm Leibniz|Leibniz]] as: either ''A'' is ''B'' or ''A'' isn't ''B''. It is read the following way: either ''P'' is true, or its denial ¬''P'' is.<ref>{{Cite book|url=http://name.umdl.umich.edu/AAT3201.0001.001|title=Principia mathematica, by Alfred North Whitehead ... and Bertrand Russell.|last=Whitehead|first=Alfred North|date=2005}}</ref>
It is also known as "''tertium non datur''" ('A third (thing) is not'). Classically it is considered to be one of the most important fundamental principles or laws of thought (along with the principles of identity, non-contradiction and sufficient reason).
<!-- == Principle as a criterion of order and classification == -->