Knowledge of God’s existence


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This topic is not about whether we can know God exists, that’s what you learn about in the philosophy topics (cosmological & teleological arguments, etc).

This topic is about what sort of knowledge Christian belief should be based on. The two main options are faith and reason.

Most theologians agree that faith should be the foundation for belief in God, but there is considerable debate over the appropriate place, if any, of reason when it comes to belief in God.

Natural theology is the theory that knowledge of God can be gained by the power of the human mind. It has two main forms:

Natural theology through reasoning about the natural world. God’s revelation is present in his creation and human reason has the ability to discover it. This resulting in knowledge of God based on reason. This is typically a catholic view.

Natural theology through sensing God is defended by some, including protestant theologians who are sceptical of the power of reason to know God.

Revealed theology is the theory that knowledge of God can be gained from God’s revelation to us e.g in Jesus and the Bible. This results in revealed knowledge which is based on faith that what is received is from God. Typically, both Catholics and protestants believe in revealed theology.

Aquinas’ Natural Theology

Aquinas accepted that human reason could never know or understand God’s infinite divine nature. However, he argued that human reason can gain lesser knowledge of God, including:

  • God’s existence: through the teleological (design) and cosmological arguments.
  • God’s moral law through natural law theory.
  • God’s nature by analogy, through the analogies of attribution and proportion.

This Aquinas a proponent of natural theology through reason, which he claimed could support faith in God.

Aquinas thought that reason could not provide an absolute proof that God existed, since that would make faith and revelation useless. He formulated a posteriori teleological and cosmological arguments which are only evidence for the Christian God that therefore support faith in God. The Bible doesn’t contain reasoned arguments for God like that.

Aquinas argued that meditating on God’s works in creation leads to us reflecting on God’s wisdom, admiring his power, having reverence for God in our hearts and love for God’s goodness in our souls. This is because if the goodness, beauty and wonder of creation, which represent a tiny proportion of God’s goodness, are so delightful to the human mind, then they will attract us even more strongly to God’s total goodness. So, natural theology can support faith.

This approach of viewing reason as a valid basis for supporting faith is typically a Catholic view:

“Faith and reason are like two wings on which the human spirit rises to the contemplation of truth” – Pope John Paul II.

Augustine & Karl Barth on Original Sin vs Aquinas’ Natural Theology

Karl Barth was influenced by Augustine, who claimed that after the Fall our ability to reason become corrupted by original sin. This is a problem for natural theology which wants to make use of reason.

Barth’s argument is that is therefore dangerous to rely on human reason to know anything of God, including God’s morality. He said “the finite has no capacity for the infinite”, meaning our finite minds cannot grasp God’s infinite being. Whatever humans discover through reason is not divine, so to think it is divine is idolatry – putting earthly things on the level of God. Idolatry can lead to worship of nations and even to movements like the Nazis. After the corruption of the fall, human reason cannot reach God or God’s morality. Only faith in God’s revelation in the bible works.

Aquinas accepts that God’s infinite nature is beyond our understanding. He is trying to claim that reason can understand the natural law God created within our nature and that some necessary being or uncaused cause exists. Nonetheless, Barth claims that reason has ‘no capacity’, i.e., zero ability, to know anything whatsoever of God. It is corrupted by original sin and therefore Aquinas’ natural theology is dangerous for relying on it.

Aquinas defends his natural theology from original sin. Aquinas claims that pre-fall human nature contained three ‘goods’:

  1. the properties of a human soul, e.g. rationality.
  2. An inclination towards the good (telos) as a result of being rational.
  3. Original justice/righteousness; perfect rational control over the soul.

Original sin completely destroyed original justice, which caused us to lose perfect rational control over our desires. Nonetheless, Aquinas argues that our rationality and its accompanying inclination towards the good was not destroyed by original sin.

Aquinas argues that only rational beings can sin. It makes no sense to say animals sin, for example. The doctrine of original sin claims that post-lapsarian humans are sinners, so, we can sin. It follows that we must still be rational beings to some degree. Our reason therefore still inclines us, through synderesis, towards goodness.

Furthermore, Aquinas diverges from Augustine, claiming that concupiscence can sometimes be natural to humans, in those cases where our passions are governed by our reason.

Aquinas concludes that original sin has not destroyed our orientation towards the good nor is our reason always corrupted. Original sin can at most diminish our inclination towards goodness by creating a habit of acting against it. Sometimes, with God’s grace, our reason can discover knowledge of God’s existence and natural moral law. So, natural theology is valid.

“Participation of the eternal law in the rational creature is called the natural law”. – Aquinas

Arguably Aquinas has a balanced and realistic view, that our nature contains both good and bad and it is up to us to choose rightly.

However, Barth still seems correct that being corrupted by original sin makes our reasoning about God’s existence and morality also corrupted. Even if there is a natural law, we are unable to discover it reliably. The bad in our nature unfortunately means we cannot rely on the good. Whatever a weak and misled conscience discovers is too unreliable.

Humanity’s belief that it has the ability to know anything of God is the same arrogance that led Adam and Eve to disobey God. Humanity believing that it has the power to figure out right and wrong is what led to the arrogant certainty of the Nazis in their own superiority. This arrogance of natural theology is evidence of a human inability to be humble enough to solely rely on faith.

Karl Barth: Aquinas’ natural theology undermines faith by making revelation pointless

If natural theology was valid then humans would be able to know God’s existence or God’s morality through their own efforts. Barth argues that would make revelation unnecessary. Yet, God clearly thought revelation was necessary as he sent Jesus. It follows that natural theology cannot be valid.

However, Aquinas insists that his natural theology does not undermine faith but instead supports it. Aquinas’ arguments for God’s existence are only intended to show the reasonableness of belief in God. They at most show that there is evidence for some kind of God. This is nowhere near strong enough to actually replace faith. The Bible doesn’t contain reasoned arguments for God like that. This is partly why Aquinas rejected the Ontological argument, since as an a priori deductive argument it sought to prove God’s existence which Aquinas worried would cause it to replace faith.

Regarding natural law ethics, although the natural law is available to everyone, Aquinas still accepts that we need revelation to gain the divine law. Similarly, regarding arguments for God, a posteriori reasoning only provides evidence that a designer or necessary being exists. Aquinas still accepts that we need faith to know the Christian God in particular exists.

The knowledge we can gain from natural theology is not the same as revealed theology and therefore cannot not replace or undermine it. If reason only has this goal of supporting faith, then it cannot make revealed theology unnecessary.

Calvin’s Sensus Divinitatis

John Calvin believed that all humans have an innate sense of the divine. Natural theology usually deals with our other senses like sight which enable us to gain knowledge of the natural world but the sense of divinity allows us to sense God’s existence. Since what we sense is not based on faith, the sense of God is natural theology. Calvin thought there was no rational way to be an atheist because of this sense. Even “backward peoples” and those “remote from civilization” have a belief that there is a God due to this sense. Calvin argued that this suggests God exists and put this sense of himself “in the hearts of all people”.

Anthropological study of the religion of tribal people remote from civilisation actually shows that they believe in magical spirits of animals and ancestors.

The extent of the spread of atheism in the 21st century suggests that this sense of God doesn’t exist. In Calvin’s time it may have been unimaginable that someone could rationally be an atheist since everyone in western societies was a believer. Even people from other countries, of whom westerners back then knew very little, believed in some sort of God. In modern times however, since David Hume there has been significant philosophical defence of atheism. In some places like northern Europe atheism is now the majority held view. Many atheists say they have no sense of God.

Plantinga defends the sensus divinitatis from the argument that not everyone has such a sense. He argues that sin has a noetic quality, meaning it changes someone’s ability to have knowledge and insight, which could block the sense of God.

Response to Plantinga: there are many atheists who are good people however. In fact, the countries with the lowest crime, the northern European countries are the most atheistic in the world. For a noetic quality of sin to explain why atheists lack a sense of God, atheists would have to sin more than Christians but that doesn’t seem to be the case. If anything, the opposite is true.

St Paul: Romans 1:20

Romans 1:20 is a bible verse which seems to justify natural theology:

“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”.

Paul here seems to suggest that God’s qualities can be understood from what he has made, i.e. the natural world. This is what inductive a posteriori arguments such as the cosmological and teleological (design) arguments do.

Calvin’s analysis of Romans 1:20

Calvin was influenced by romans 1:20  but attempted to explain how it justifies natural theology without using human reason, i.e. the sensus divinitatis.

However, what about the word ‘understood’ – doesn’t that imply reasoning rather than merely sensing? Furthermore, the verse seems to suggest that the understanding is gained from creation itself, which sounds like reasoned inference from the natural world rather than a sense of God which isn’t derived from ‘what has been made’; creation. Finally, the verse suggests that God’s qualities and nature can be understood – not just his existence, so it seems to go further than the sensus divinitatis in that regard also.

Barth’s analysis of Romans 1:20

Barth responds to the claim that Romans 1:20 justifies natural theology with an alternative interpretation of it as being against natural theology. He accepts that the passage shows that creation does indeed allow knowledge of God, but argues humans are too sinful to manage that. Barth points to Romans 1:25 where St Paul warned, regarding the Gentiles (a non-jew), that “They exchanged the truth about God for a lie, and worshiped and served created things rather than the Creator”. Barth claims that Paul is showing that natural theology leads to idolatry – the worshiping of fake idols where, due to overlooking or misunderstanding the ‘qualitative distinction’ between humans and God, God is experienced in natural things like birds, and then in humans and half-spiritual things like Nation or Fatherland.

Grenz and Olson describe Barth’s view: “Any attempt to ground the truth of God’s Word in human reasoning, however devout and sincere, inevitably leads to theology being subverted by human, historical modes of thought and thus to ‘anthropocentric theology’. The evil against which Barth fought so hard.”

The ‘evil’ referred to here is Nazism, the influence of which on Christianity Barth resisted.

Who is capable of knowing God through his creation, if not us? The bible claims that knowledge is possible, so presumably there must be some being who can manage it. Barth claims that our reason is too corrupted and ‘fallen’ for it to apply to us, but arguably a better interpretation of the idolatry point from Romans 1:25 is that it is a warning that understanding God through the natural world can sometimes lead to idolatry and that we should be careful of that danger.


Furthermore, the final part of the passage: ‘so that people are without excuse’ clearly refers to us – people born after the fall. So, the passage must be about us.

Calvin’s revealed theology 

Calvin was influenced by Augustine’s views on the fall and original sin. The garden of Eden is God’s intended design for the world as a paradise. The suffering brought into the world by the fall therefore disfigures the world to an extent, which makes it difficult for natural theology to reveal God since his original design is now mixed with disfiguring corruption. This means natural theology can only reveal the truth of God’s existence, but not the full revelation of God. However, Calvin is clear that knowledge of God is not simply a matter of knowing that God exists:

“We know God, not when we merely understand that there is a God but when we understand … what is conducive to his glory”.

This means we only truly know God when we know how to glorify God through worship and following God’s moral commands. Natural theology cannot achieve that knowledge. Jesus was God revealing himself and the Bible is a record of that revelation. We therefore require revealed theology; faith in Jesus and the Bible to have the full revelation of God’s existence. Calvin argued that people should see their mind as nothing more than a passive reception of the revelation of the Bible.

Calvin and Barth rely on the classic protestant argument that we should not rely on reason to understand anything about God or God’s morality because original sin has corrupted our reason. We should just have faith in the Bible and that should be our only source of knowledge about God’s existence or morality. This argument relies on a traditional view of original sin that goes back to Augustine, that human nature is corrupted, including our ability to reason.

Defending natural theology through reason against original sin

Natural theology through reason could be defended by denying the existence of original sin. Original sin being a totally false doctrine is very unpopular position in traditional Christianity but there are some serious theologians who hold that position, such as Pelagius and some liberal Christians. Liberal Christians would argue that the scientific evidence suggests that we cannot take the genesis story of creation, including the fall, as literal events. In that case, Augustine cannot be correct in claiming that humanity was cursed by original sin.

Note that this is not the approach taken to defending natural theology through reason by Aquinas or Bruner, whose approach instead is to attempt to reconcile original sin with natural theology.

However, many theologians who don’t agree with Augustine about a literal fall or original sin being inherited still hold to the doctrine of original sin. Augustine could be defended that his views on human nature can be derived from the evidence of his observations of himself and his society. For example, Augustine told a story about how, as a child, he stole a pear from a garden, not because he was hungry but just for the pleasure of sinning. He concluded even children desire to sin and so must be born that way. Concupiscence can also be observed: people have their own will overwhelmed by bodily desires, which Augustine takes to be evidence for original sin.

Pelagius: Augustine’s observations reflect his society, not human nature. Pelagius goes further than Aquinas and Brunner however and completely denies the Augustinian doctrine of original sin.

“The long habit of doing wrong which has infected us from childhood and corrupted us little by little over may years and ever after holds us in bondage and slavery to itself, so that it seems somehow to have acquired the force of nature”. – Pelagius

Although it might appear that we have strong forces within us that incline us toward evil, Pelagius argues that could simply be because of the way we are raised and it only appears to be our nature because of how thoroughly corrupted we are by our upbringing, which Pelagius refers to as being “educated in evil”.

We could add contemporary historical and sociological evidence to Pelagius’ point. Humans have progressed since Augustine’s time. Martin Luther King said, “the arc of the moral universe is long, but it bends towards justice”. Steven Pinker attributes to the power of human reason that violence has decreased, even considering the 20th century. The average human life seems more secure than at any prior point in history. If Augustine were correct that original sin caused an irresistible temptation to sin, then human behaviour could not have improved, yet it has. Original sin is therefore a false doctrine and human reason is not corrupted.

Emil Brunner 

Brunner argues that Augustine and Calvin are wrong to think that the fall destroyed the potential of human reason to gain knowledge of God’s existence. Brunner claimed the fall destroyed the material imago dei (Adam and Eve’s relationship with God) but not the formal imago dei, which is what separates us from animals and gives us language, reason and moral responsibility. This is corroborated by Psalm 8 which states humans are lower than the angels but higher than the animals. Humans still have rationality and language and are thus different to animals, so we must still have something of the formal imagio dei; it cannot have been completely destroyed by the fall.

The natural knowledge Brunner claims can be gained through reason is knowledge of preserving grace – that God continues to be active in maintaining creation, shielding it from the effects of sin. This can be known through the order in the universe; that the world is still spinning, and humans still existing reveals God’s gracious preservation of us. Brunner still thinks however that natural theology alone will always, due to our sinful state, result in a distorted knowledge of God. We need the special revelation of Christ to achieve full knowledge.

Barth claims that Brunner contradicts himself since Brunner admits every aspect of humanity is corrupted by sin, so it should follow that the formal image, including our reason, is corrupted, in which case arguably it cannot produce knowledge of God. Just because reason was not totally destroyed, it being corrupted still means it cannot be relied on to gain knowledge of God.

Possible exam questions for knowledge of God’s existence

Can God be known through reason alone?
Is faith sufficient for belief in God?
Assess the possibility of natural knowledge of God’s existence.
Assess whether revealed knowledge of God’s existence is the only valid type.

Assess whether the Fall completely removed all natural human knowledge of God
Is faith in God’s revelation in Jesus required to know God?
‘Human sin and finitude prevents natural knowledge of God’ – Discuss.
Can God be known through his creation?
Does God’s creation reveal his beauty, goodness, design and purpose?

Is natural knowledge of God the same as revealed knowledge?
Is belief in God’s existence sufficient to put one’s trust in him?
What is the human intellect capable by itself of discovering about God?

Quick links

Year 12 Christianity topics:
Augustine. Death & afterlife.
Knowledge of God’s existence. Person of Jesus.
Christian moral principles. Christian moral action.

Year 13 Christianity topics:
Pluralism & theology. Pluralism & society.

Gender & society. Gender & theology.
Secularism. Liberation theology. 

OCR Ethics
OCR Philosophy
OCR essay structure
OCR list of possible exam questions