Editing Cosmological argument (section)

=== Aquinas's argument from contingency ===

In the [[scholasticism|scholastic]] era, [[Aquinas]] formulated the "argument from [[Contingency (philosophy)|contingency]]", following [[Aristotle]], in claiming that [[Unmoved mover|there must be something to explain the existence of the universe]]. Since the universe could, under different circumstances, conceivably ''not'' exist (i.e. it is contingent) its existence must have a cause. This cause cannot be embodied in another contingent thing, but something that exists by [[INUS|necessity]] (i.e. that ''must'' exist in order for anything else to exist).<ref name=Aq5w/> It is a form of argument from [[universal causation]], therefore compatible with the conception of a universe that has no beginning in time. In other words, according to Aquinas, even if the universe has always existed, it still owes its continuing existence to an [[Primum movens|uncaused cause]],<ref>Aquinas was an ardent student of Aristotle's works, a significant number of which had only recently been translated into Latin by [[William of Moerbeke]].</ref> he states: "...&nbsp;and this we understand to be God."<ref name=Aq5w/>

Aquinas's argument from contingency is formulated as the [[Five Ways (Aquinas)#Third way: The Argument from Time and Contingency|Third Way]] (Q2, A3) in the ''[[Summa Theologica]]''. It may be expressed as follows:<ref name=Aq5w/>

#There exist contingent things, for which non-existence is possible.
#It is impossible for contingent things to always exist, so at some time they did not exist.
#Therefore, if all things are contingent, then nothing would exist now.
#There exists something rather than nothing.

He concludes thereupon that contingent beings are an insufficient explanation for the existence of other contingent beings. Furthermore, that there must exist a ''[[INUS|necessary]]'' being, whose non-existence is impossible, to explain the origination of all contingent beings.

<ol start="5"><li>Therefore, there exists a necessary being.</li>
<li>It is possible that a necessary being has a cause of its necessity in another necessary being.</li>
<li>The derivation of necessity between beings cannot regress to infinity (being an essentially ordered causal series).</li>
<li>Therefore, there exists a being that is necessary of itself, from which all necessity derives.</li>
<li>That being is whom everyone calls God.</li></ol>