Blog for Aquinas

Aquinas’ first way is about actuality and potentiality – he gets these ideas from Aristotle.  Now is a good time to revise Aristotle!!  It is called the unmoved mover.  Aquinas says that things are in motion – by which he means things change.  For example, something cold has the potential to become hot and vice versa.  Something cold cannot become hot on its own; it needs something already hot to make it hot.  The cold thing is dependent on the hot thing to make it hot.  The idea works the other way round as well.  For example, a hot thing has the potential to become cold.  Aquinas puts it like this, “But nothing can be reduced from potentiality to actuality, except by something in a state of actuality.  Thus, that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot and thereby moves and changes it.”

This argument isn’t about how the universe began; it is about the continued changes we see in the universe.  It is about dependency - things being dependent upon other things for change.  Aquinas is saying that because things cannot reach their actuality on their own, they need the continued existence of some other thing that moves (changes) them.  And this thing ultimately is God.

Aquinas’ second way is the uncaused causer and is about efficient cause.  Again he gets this straight from Aristotle.  Remember that efficient cause is about the agent that makes something.  Your efficient cause is you mum and dad (nice thought…?)  Things can’t be their own efficient causes, you can’t create yourself.  Aquinas puts it like this, “Now to take away the cause is to take away the effect.  Therefore if there be no first cause amongst efficient causes, there will be no ultimate or no intermediate causes…therefore it is necessary to admit a first efficient cause, to which everyone gives the name God.

Aquinas’ third way is about contingency and necessity.  Everything in the physical world is contingent, in other words things need other things to bring them into existence.  Nothing would ever have even started unless there was another thing to bring it into existence.  The means there must be a being that is not contingent on something else for its existence, it must be independent of everything else...God!

A key point here is that if everything exists contingently then it must be possible to have a time when nothing existed.  If so and there was another time when nothing existed – then there would be nothing to bring anything into existence, or there must be something, the existence of which is necessary and which cannot fail to exist.

Get it!!?