Knowledge of God’s existence A* grade summary notes


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Aquinas’ Natural theology

  • Aquinas thinks that human reason has the ability to figure out things about God. 
  • God’s infinite nature is beyond our understanding, but we can figure out some lesser truths about God. 
  • We can’t know exactly what God is, but we can at least know God’s morality and that God exists: 
  • God’s natural moral law – through natural law ethics
  • God’s existence – as the required explanation of the existence of the universe through the cosmological argument, and as the required explanation of the nature/design of the universe through the teleological argument.
  • This tends to be the catholic view. JP II said that faith and reason are like two ‘wings’ with the human spirit rises to know the truth.


  • Karl Barth’s critique of Aquinas’ natural theology
  • Humans are too corrupted by original sin – including our reason. 
  • So, it’s dangerous to rely on human reason to know anything of God, since it is corrupted by original sin. 
  • Therefore, we should not rely on reason, we should just rely on faith to know God. 
  • Barth is recommending revealed theology exclusively.

Defence of Aquinas

  • Aquinas responds that original sin cannot have completely destroyed the orientation towards the good that the image of God gives us.
  • It destroyed our ability to have perfect rational control by giving us temptations to sin.
  • However, the fact that we still have some rationality and can sin at all shows that original sin has not lowered us to the level of animals. The image of God is what separates us from the animals and it must still exist in us and orient us towards knowing God and his moral law, even if our ability to act on it has been lessened.

Optional further evaluation

  • Karl Barth also makes the  critique that natural theology causes reason to replace faith. 
  • If we could know God through our own reason, then that would make it pointless for God to reveal himself. 
  • Yet God clearly did reveal himself through Jesus – so we must not be able to figure everything out by ourselves. 
  • If we could know God through reason then faith would be useless.

Optional defence of Aquinas 

  • Aquinas insists that his natural theology is not replacing faith. He accepts that we need faith and revelation to know most things about God – nonetheless there are some things that reason can tell us e.g. natural law ethics and God’s existence. 
  • This shows that reason can strengthen faith but does not replace it.

Calvin’s sensus divinitatis 

  • Calvin was a protestant but was unusual because he defended a form of natural theology. 
  • He agreed with the protestant argument that reason is corrupted and unreliable, but he still thought there was a way for the human mind to know God exists without faith.
  • All humans are born with the ability to sense that God exists – an innate sense of the divine. 
  • This is a form of natural theology because it involves knowing God exists but due to sensing God, not due to faith.
  • Both Calvin and Aquians say the human mind can know God exists by itself – but Aquinas says this is due to human reason, Calvin disagrees with that – saying it is due to an innate sense of God.

Evaluation of the sensus divinitatis

  • Atheists do not have a sense of God – it’s something that is taught to people, they aren’t born with it. 
  • In Calvin’s time everyone was forced to believe in God, so it’s easy to see how Calvin would think everyone is born knowing God exists.
  • However, with the rise and spread of atheism, some countries are majority atheist now.
  • It doesn’t look correct that people are born with a sense of God’s existence.

Optional further evaluation

  • Plantinga defends the sensus divinitatis from this criticism, arguing that sin could have a noetic effect, meaning it could interfere with and prevent the sense of God.

Optional final evaluation:

  • However, there is no evidence that sin is more common amongst atheists, in fact if anything the evidence suggests that atheistic countries have the lowest crime rates in the world.

St Paul Romans 1:20

  • Romans 1:20 is a bible verse which seems to justify natural theology.
  • It says that God’s nature/qualities can be understood from the natural world.
  • “Since the creation of the world God’s invisible qualities – his external power and divine nature – have been clearly seen, being understood from what has been made, so that people are without excuse”.
  • This sounds like it justifies Aquinas’ natural theology – his arguments for God – teleological/cosmological – because they involve reasoning about creation – the natural world – and concluding that God exists.


  • Calvin’s interpretation of Romans 1:20/
  • Calvin doesn’t think this quote backs up Aquinas’ version of natural theology – he thinks it’s only backing up his version – the sensus divinitatus God. 
  • This quote is just saying that everyone has a sense of God.

Further evaluation

  • However – quote explains that God’s ‘qualities’ and ‘nature’ can be understood – not just God’s existence. 
  • It also says that God is understood ‘through’ creation – not merely through having a sense of God. So, Calvin’s interpretation is a disaster.

Further evaluation

  • Karl Barth also attempts to make a revealed-theology compatible interpretation of romans 1:20. 
  • He argues that even if the quote is correct that God can be understood through creation, that doesn’t mean we corrupted post-lapsarian humans are capable of doing that.

Further evaluation

  • However, Barth’s interpretation is not credible.
  • The passage explains the purpose of knowing God through creation is so that people are ‘without excuse’, so it’s hard to see how it could apply to anyone except post-lapsarian humans.