Aquinas' cosmological argument

• Created by Thomas Aquinas - a 13th century Catholic priest
• It is an Aposteriori argument because it uses evidence to reach conclusions
• Aquinas has five ways - Way 1 is his argument from motion and change, way 2 is his argument from causation and Way 3 is his argument from contingency and necessity
• Contingency - The idea of something being dependent on something else to exist
• Necessity - The idea that something must exist for all other things to be able to exist
• Aquinas argued that something can only be possible because it has happened. Therefore, it is possible that there was a time where nothing existed
• Everything can exist or not-exist. Everything in the natural world is contingent. If everything is contingent then once upon a time there as nothing. If there was once nothing, then nothing could come from nothing. Therefore, something must exist necessarily
• Everything necessary must be caused or uncaused. But the series of necessary beings can't be infinite, because there would be no explanation for the beginning of the series. Therefore, there must be something uncaused which exists of its own neccesity. This must be God
• Aquinas observed that everything in the universe has a cause. It is illogical to argue that this chain of clauses go back forever (uncaused cause and unmoved mover). Aquinas concluded that there must be an uncaused cause, and this is the God of classical theism.
• Weaknesses of the cosmological argument

  Aquinas has committed the "Fallacy of Composition" - because he has observed one part of the universe he presumes that the therefore the whole universe acts in that way
• Weaknesses of the cosmological argument


  Hume argues that talk of God is meaningless because it cannot be worked out through logic alone. Aquinas makes "synthetic" statements and not "analytic" propositions
• Weaknesses of the cosmological argument

  If it is possible that at one point in time nothing existed, it is possible that God also did not exist
• Weaknesses of the cosmological argument

  Hume argues that the universe itself could be the necessary being - why does it need a God to create it?
• Weaknesses of the cosmological argument

  Russell - The universe exists as a "brute fact" and is unexplainable
• Weaknesses of the cosmological argument

  There could be a group of necessary beings, not just one. There could also be a group of uncaused necessary beings.
• Weaknesses of the cosmological argument

  Why can't the universe itself be eternal and uncaused. For example, the universe already existed but the Big Bang created the world inside it
• Strengths of the cosmological argument

  Aquinas does not commit fallacy of composition, instead he uses classic aposteriori reasoning - drawing the most likely conclusion from what he observes
• Strengths of the cosmological argument

  Aquinas argues the case for God's metaphysical necessity, not his logical necessity
• Strengths of the cosmological argument

  Aquinas argues that God is not like other beings, because he is the only uncaused necessary being
• Strengths of the cosmological argument

  Hume's argument further proves the case for a necessary being being logically sound - why not God instead of the universe
• Strengths of the cosmological argument

  Science assumes that there is no "brute fact". So therefore, Russell's argument is illogical
• Strengths of the cosmological argument

  Occam's razor - The belief in one uncaused being is simpler, so is the right answer
• Strengths of the cosmological argument

  No scientific theories explain why there is something other than nothing
• Aquinas' Way 1


  Way 1 is his argument from motion and change
• Aquinas' way 1


  He drew from Aristotle’s observation that each thing in the universe that moves is moved by something else. ​Aristotle argued that everything begins with a 'primary mover' that had not itself been moved or acted upon by any other agent. ​Aristotle called this mover 'God'
• Aquinas' way 2 


  Way 2 is his argument from causation 
• Aquinas' way 2 


  Again, this builds up on Aristotle's ideas about notion of an efficient cause, the entity or event responsible for a change in a particular thing.​ Every efficient cause must itself have an efficient cause and because there cannot be an infinite chain of efficient causes, there must be an first cause of all the changes that occur in the world, and this first cause is God.​
• Hume and Russell both rejects the claim that any being can be necessary​. Any being who exists can also not exist. There is no contradiction in thinking that any being does not exist. This is true of God also, because there is no contradiction in saying 'God does not exist'
• Russell argues that Way 3 commits the Fallacy of composition


  Russell is aiming criticism at Way 2 and 3. Aquinas' says everything single event in the universe has a cause so, the universe as a whole has a cause. Russell rejects it completely and says there is no reason why we can't argue every single event in the universe has a cause, but the universe itself is uncaused. Russell's logic can also be applied to Way 3. For Russell, this commits the fallacy of composition, because everything in the universe may be contingent, but the universe as a whole is necessary ​
• Hume suggests that the universe itself may be a necessarily-existent being​. This would be an adequate explanation without having to bring God into it.
• Aquinas' way 3 


  Aquinas observed the universe and saw that everything had a limited lifespan, he therefore concluded that there is no contingent being that is everlasting. This means that at some point, before contingent beings, there must have been nothing in existence. Therefore, something must exist necessarily. And by this, we all understand God.