Knowledge of God’s existence


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.

Calvin’s Sensus Divinitas

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.

Feuerbach argued that a universal belief in God only suggests a universal human psychological need for a God.

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.

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

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 divinitas in that regard also.

Barth responds with an alternative interpretation of romans 1:20 as being against natural theology, that while creation does indeed allow knowledge of God, 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.

Arguably Romans 1:20 it is simply referring to Adam and Eve, before they were corrupted by original sin. This would fit with Barth’s claim about original sin being what corrupted human reason.

What about ‘so that people are without excuse?’ That surely refers to people born after the fall.

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.

The issue of original sin. 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.

Aquinas and Brunner’s approach to defending Natural theology through reason is to try and reconcile original sin and some ability for reason to support faith in God’s existence & morality. However, there is another way to defend natural theology from original sin, which is to simply deny the existence of original sin. This is not a popular view 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. 

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. “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.

Aquinas’ Natural Theology

Aquinas believed that human reason could never know or understand God. However, Aquinas is a proponent of natural theology through reason which he claimed could support faith in God. Human reason can gain knowledge of:

  • God’s existence: through the teleological (design) and cosmological arguments.
  • God’s natural moral law through the ability of human reason to know the synderesis rule and primary precepts.
  • God’s nature by analogy, through the analogies of attribution and proportion.

Aquinas thought that reason could not provide an absolute proof that God existed, since that would make faith and revelation useless. This is why he rejected the deductive ontological argument but accepted and formulated teleological and cosmological arguments which are only inductive evidence for the Christian God, not conclusive proofs, which therefore support faith in God.

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.

Karl Barth argued that Aquinas’ natural law theory was a false natural theology which placed a dangerous overreliance on human reason. Barth argued that if humans were able to know God or God’s morality through their own efforts, then revelation would be unnecessary. Yet, God clearly thought revelation necessary as he sent Jesus.

Barth also argued that “the finite has no capacity for the infinite”; our finite minds cannot grasp God’s infinite being. Whatever humans discover through reason is therefore not divine so to think it is must then amount to idolatry – the worship of earthly things. Barth argued idolatry can lead to worship of nations and then even to movements like the Nazis. It follows for Barth that after the corruption of the fall, human reason cannot reach God or figure out right and wrong by itself. Only faith in God’s revelation in the bible is valid.

In defence of Aquinas, he is not suggesting that our finite minds can understand God’s nature or goodness (eternal law). Aquinas is only suggesting that reason can understand the natural law God created within our nature and that some necessary being or uncaused cause exists. If reason only has this goal of supporting faith in such ways, then it cannot make revealed theology unnecessary.

 Tillich defends Aquinas to a degree, arguing that Barth was too negative in denying the possibility of reason discovering anything whatsoever of the natural law.

“there is self-deception in every denial of the natural moral law … The very statement that man is estranged from his created nature presupposes an experience of the abyss between what he essentially is and what is existentially is. Even a weak or misled conscience is still a conscience, namely, the silent voice of man’s own essential nature, judging his actual being” – Tillich.

To deny that our conscience can discover the natural law is to claim that there is a gap between what we currently are and what we could be. Yet, to have an awareness of that gap is to have a conscience that is aware of its fallen state. So it is contradictory to deny the natural law. Even it now involves a weakened conscience, that still tells us at least something of the direction we have fallen in and the direction back towards righteousness.

However, whatever a weak and misled conscience discovers is surely not God’s morality. Humanity believing it has the ability to know anything of God is the same arrogance that caused 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. The arrogance of natural theology is evidence of a human inability to be humble enough to simply have faith.

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.

Aquinas vs Augustine on original sin & natural law

Aquinas thinks that human reason has the power to understand the natural law in our human nature, which is orientated towards the good thereby allowing us to act morally. This amounts to a considerable disagreement with Augustine, who thought that both human nature and reason were too corrupted by original sin to follow the natural law. For Augustine, the only thing humans have for moral guidance is the divine law as revealed in the Bible, such as the command to love your neighbour as yourself. Even then, according to Augustine, original sin is so corrupting only a person who happens to have been mercifully and undeservedly gifted grace by God will be able to be morally good.

Aquinas disagrees with Augustine’s view of 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. Our inclination towards good is due to our rationality and since only rational beings can sin, sin cannot destroy our inclination towards good, but it can diminish it through creating a habit of acting against it.

Augustine conceives of original sin as a corrupting force that corrupted our nature, whereas Aquinas conceives of original sin as merely a lack of original justice. This explains why Aquinas doesn’t think that original sin is as destructive to human nature and reason as Augustine does, leaving Aquinas open to conclude that human reason can provide partial knowledge of God’s existence and morality. “Participation of the eternal law in the rational creature is called the natural law”. Arguably Aquinas has a balanced view, that our nature contains both good and bad and it is up to us to choose rightly.