
Natural theology is a type of theology that provides arguments for the existence of God based on reason and ordinary experience of nature. It is the science of God insofar as He is accessible to natural reason; insofar as we can infer knowledge about God from the natural order.
History[]
Since Gottfried Wilhelm Leibniz, natural theology has also been known as the less appropriate name of "theodicy" ("justifying God"), originally meaning "justifying God's existence, given the existence of evil." In the Western religions, the knowledge of God can be classified through revealed theology (knowledge through grace and revelation) and natural theology (using natural reason to come to God). Typical of natural theology have been the traditional philosophical proofs of God's existence, such as the ontological, cosmological, and teleological arguments, as well as Immanuel Kant's less-proved moral argument. Most of the arguments rely on at least one empirical premise.
Ontological argument[]

It is called the ontological argument because it infers God's existence from what it means to be God, of from the definition of God; it arrives at God's existence purely through rational reflection. There are several different versions, all of which purport to show that it is self-contradictory to believe that there is a greatest possible being. The statement "there is no God" is held to be an absurdity and a self-contradiction. The argument argues that it is a necessary truth that this being exists.
Anselm of Canterbury[]
The first and most successful author of the argument was Archbishop Anselm of Canterbury. He argued, in 1078, that God is "that than which nothing greater can be thought", and argued that this being must exist in the mind, even in the mind of the person who denies the existence of God. He suggested that, if the greatest possible being exists in the mind, it must also exist in reality. If it only exists in the mind, then an even greater being must be possible - one which exists both in the mind and in reality. Therefore, this greatest possible being must exist in reality, meaning that God exists. To come to any other conclusion is a self-contradiction. The argument was powered by the ideas of having a coherent being that instantiates all perfections, that there is a coherent idea of a being that bestows "great-making" properties, and that existence is a perfection or a "great-making" property. Even in Anselm's lifetime, his argument was challenged (rather poorly) by the monk Gaunilo of Marmoutiers, who came from one of the most distinguished centers of learning in Europe, Marmoutiers Abbey. He believed that Anselm's argument too easily moved from the existence of an idea to the thing that corresponded the idea, claiming that Anselm defined things into existence. Gaunilo worried that one could use Anselm's argument to justify the existence of nonexistent things, such as "an island in which none greater can be conceived." The "perfect island" argument could be easily refuted, as its shore might arbitrarily be increased and decreased, varying with the tide; it is always possible to imagine a bigger physical island, but not any greater thing than God. There is no intrinsic maximum for the size of an island, while there is no greater being than God. Gaunilo did not understand Anselm's point, and Anselm easily rebutted him.
Thomas Aquinas[]

While Thomas Aquinas believed that God's existence is self-evident, he rejected Anselm's argument. He argued that not everyone who hears the word "God" understand that it signifies a thought, with others seeing God as a body. Since people have different ideas of what God is, there is a problem concerning Anselm's argument.
He had problems with the ontological argument. On his view, even if we assume that everyone shares the same concept of God, it does not therefore follow that he understands what the word "God" signifies exists actually, but only that exists mentally. One natural interpretation of the ambiguous passage is that Aquinas rejected Anselm's second premise, saying that humans have no idea what the sequence of words "A beigng that which none greater can be conceived" really means, saying that God is unlike any other reality known to us.
The success of the argument does not depend on our having a complete understanding of the concept of a being that which none greater can be conceived. While we do not have a complete understanding of the largest number, it can be said that there is no such number. If the concept is coherent, than even a minimal understanding of the concept is sufficient to make the argument. Therefore, Anselm's argument survived both Gaunilo and Aquinas' criticisms.
Immanuel Kant[]

Immanuel Kant made the most damaging criticism. He directed his criticism at the third premise's claim that a being that exists in both the mind and reality is greater than a being that exists as an idea in the mind. Kant argued that existence does not function as a property, and that "being is evidently not a real predicate... It is merely the positing of something... Logically, it is merely the copula of a judgment." Kant argued that, if God "is", there is no new predicate added to God, instead confirming his conception. What goes wrong with the first version of the argument is the notion of existence being treated as the wrong logical type. Concepts as a logical matter are entirely in terms of logical predicates. Since existence is not a logical predicate, it does not belong to the concept of God. Kant's argument makes a plausible metaphysical point, arguing that existence is not a property in the same way that an apple being red is a property; it is instead a precondition. "Nothing" has no qualities whatsoever, so existence is not a "great-making property", as it is not a property at all, instead being a metaphysical instantiation for the existence of properties.
There are two different versions of the ontological argument in Anselm's Proslogium, with the second version not relying on the highly-problematic claim that existence is a property, thereby avoiding the rejections of his argument by Kant. The second version claims that God exists so truly that it cannot be conceived not to exist, that God is a being that which a greater being cannot be conceived, and that necessary existence is a property. A being that necessarily exists in reality is greater than one that does not, meaning that God existing as an idea in the mind but not necessarily in reality, something greater can be conceived. Since there is nothing greater than God, he therefore also exists in reality. It is this second part of the argument that prevents Kant from completely destroying Anselm's original argument.
Descartes[]

560 years after Anselm made his argument, Rene Descartes began to compose several ontological arguments. In his Fifth Meditation, he said that the mere fact that he could produce thought meant that the idea of God is an idea that can be found within the human mind, just as any shape or number. Descartes argued that God's existence could be deduced from his nature, just as geometrical ideas could be deduced from the nature of shapes. He assumed that existence was a predicate or perfection; thus, if the notion of God did not include existence, it would not be supremely perfect. Consequently, the concept of a supremely perfect of a God who did not exist would be unintelligible; God had to exist.
Cosmological argument[]
In Thomas Aquinas' Summa Theologica, he argued his quinque viae ("five ways"). The five ways were five cosmological arguments regarding the existence of God, and they were meant to constitute together a singular grand argument:
- The way of the unmoved mover - God causes changes
- The way of the first cause - It is not possible for something to be the cause in itself, meaning that God causes everything, being as he is at the start of the chain
- The way from contingency - If everything were contingent (perishable things), nothing would exist at one point, with an imperishable and necessary being (God) causing things to exist.
- The way of degrees from perfection - God causes things to be perfect or imperfect
- The way from design (teleological argument) - Behavior and development is caused by God
Besides presenting them in the Summa Theologica, he expanded upon the first three in the Summa Contra Gentiles. He believed that people can infer God's existence from the effects best known to us. He argued that God caused the changes in the world, and that a potential in the world could not cause itself to exist, meaning that it could only be caused by something already existing (God).
Hume and Kant[]

The theory was criticized by both David Hume and Immanuel Kant. Kant was the more serious of the two, arguing that our minds give structure to the raw materials of reality, and that the world is divided between the nominal and noumenal worlds. Since the noumenal world is beyond our knowledge, we cannot know what is there, and the cosmological arguments fail due to insisting that the noumenal world is somehow coherent to humans (despite it being noumenal).
Hume had rejected the argument by rejecting causation altogether, misunderstanding Aquinas' intent. Aquinas argued for a cause that is first in a hierarchy, while Hume mistakenly assumed that the cause was the first in a sequence.
Teleological argument[]
William Paley and the intelligent design movement argued that objects in the world do not have inherent dispositions or ends, but that God gives things a purpose. Paley argued that if we should come across a watch, we would not assume that it had always been there, and that such an object required an explanation. Paley said that we should assume the same for the Earth as well, which also required explanation.
Moral argument[]
Kant thought that metaphysical proofs of God's existence were doomed to failure due to their attempts to penetrate noumena by pure reasoning; noumena was beyond the limits of understanding. In his Critique of Practical Reason, Kant held that belief in God's existence was necessary as mankind's attainment of the highest good, and that it was necessary for morality. He argued for justice in the afterlife, but this has been equated to believing in God's existence.
Problem of evil[]

Epicurus
The problem of evil is the favorite argument of atheists, who claim that the presence of evil in the world means that God does not exist. There are the logical and evidential forms of the argument, with the logical argument attempting to claim that evil and God can coexist, while the evidential argument posits that it is probable that there is not an omniscient God.
Logical argument[]
Using the logical argument, Epicurus stated that if there is a benevolent God, that evil must not exist. Because evil exists in the world, he argued, God could not exist. An omnipotent being could prevent evil from coming into existence, just as any benevolent being would. Because evil exists, the theory of a benevolent God would end in a logical contradiction.
Most philosophical debates revolve around the coexistence of God and evil. Kant believed that God could allow for evil to exist to achieve a greater good, justifying evil's coexistence. Some philosophers believe in distheism, believing that God is not wholly good; others believe that he is not entirely all-powerful. Most theists would disagree with these points.
Evidential argument[]
The evidential version says that there is a lower probability of theism due to evil's existence. Versions of the evidential argument include William Rowe and Paul Draper's arguments. Rowe believed that an omniscient and good being would prevent suffering, unless preventing bad would mean the loss of a greater good. Therefore, a benevolent and omniscient being could not exist. Draper argued that if there are supernatural beings, they are indifferent to gratuitous evils, making a better explanation than theism. The evidence prefers that no God, as commonly understood by theists, exists.
Responses to the Problem of Evil[]
Responses to the Problem of Evil have been called "defenses" or "theodicies". A defense attempts to defuse the logical problem of evil, while a theodicy is more ambitious, attempting to provide a plausible justification for the existence of evil, and thus rebutting the evidential argument. Richard Swinburn says that it does not make sense to say there are greater goods without naming what they are; a successful theodicy cannot exist unless the greater goods are named.
There are several responses to the Problem of Evil, namely:
- Greater Good - asserts that God allows evil to happen in order to prevent a greater evil, or to encourage a response that will lead to a greater good. It is seen as devaluing suffering and not addressing the premise that God is all-benevolent, and therefore should be able to stop all evil rather than playing a balancing act.
- Free Will Defense - Without humanity being given free will, we would live without freedom, something that in itself is evil. God would not rid humanity of free will, and humans are responsible for their own actions.
- Soul-Making - Created by Greek cleic Irenaeus, who argued that human creation comprised humans being made first in the image of God (having the potential to achieve moral perfection), and then the likeness of God (the achievement of that perfection). To achieve that perfection, a person must achieve free will; to achieve free will, humans must experience suffering.
- Heaven Swamps Everything - Suggested by Thomas Aquinas; being an afterlife that is unending while human life is short outweighs the evils of life. Early theologian Origen believed in apocatastasis, universal salvation, and he therefore believed that God could not suffer a single defeat or lose a single soul. He therefore believed that the world of suffering and Hell were penitentiaries, places to endure suffering for the purpose of spiritual purification.
- Privation Theory - Evil is a defect in something otherwise good; a lack/privation of goodness. Clement of Alexandria (teacher of Origen) was a proponent of this theory, saying that evil exists as a negative. Augustine of Hippo argued that evil was created when Adam and Eve defied God, and that humans have an inclination towards sin that has deprived them of the original goodness, form, order, and measure.
- Evil as Illusory - Christian Science view; evil and sickness are illusions.
- Finite God Theodicy - God may not be all-powerful, or cannot prevent genuine evil (despite being almighty).
- Hidden Realms and Other Minor Theodicies - Asserts that there exists the logical possibility of hidden or unknown reasons for the existence of evil and an almighty, all-knowing, benevolent God.
- Is a Perfect World Possible? - Leibniz believed that this world was as perfect as it could be, a view criticized by Voltaire.
Theodicy[]
Theodicy, meaning "justifying God", is a term coined by Gottfried Wilhelm Leibniz in 1710. Defined by A. Plantinga as the answeer of the question of why God permits evil, it is a theological construct that attempts to vindicate God in response to the evidential problem of evil. People faultily assume that a perfect world is possible, but something that is created can always be more perfect.
Personal Immortality[]
There are three models for personal immortality:
- Survival of Astral Body - Even if the physical body decomposes, the astral body survives; commonly depicted in art (i.e. King Hamlet's ghost). As ghosts appear in clothes, this would frivolously mean that there are also astral clothes.
- Immaterial Soul - Humans are made up of two substances: the body and the immaterial soul. A minority believe that souls are located in space, as any object takes up space. Since the 17th century, most people believe that the mind and soul are one.
- Resurrection - Jews, Christians, and Muslims believe that the soul detaches from the body upon death and exists in an incorporeal state until the moment of resurrection. A minority believe that there is no intermediate state between death and resurrection.
Philosophical views on immortality[]
There are also several philosophers who argued for belief in immortality, namely:
- Blaise Pascal - "Pascal's Wager" thought experiment, arguing in favor of belief of God's existence and immortality. If we are to decide to believe whether God exists or not, it is wise to believe that He exists; if we believe that he exists, we gain eternal bliss, while we neither gain nor lose nothing if we do not believe in God's existence (and, if he does exist, we will suffer in Hell). By calculations of risks and benefits, we should believe in God.
- Kant - Had a "Moral argument" for God's existence, arguing that belief and God in immortality is a prerequisite for moral action. If people do not believe in a final judgment, there will be no motivation to be good. There is also a need to find meaning in life, another pragmatic argument.
- Plato - The first philosopher to argue for both the convenience and the truth of believing in immortality. In his work Phaedo, he argued that people remember knowledge from past lives; we know things that are not available to us. The knowledge of equality is innate, as we already recognize that two sticks are not the same; this is an argument for the transmigration of souls.
Dualism[]
Dualism is the belief that the human consists of the body and soul. Most Duallists belive that the mind and soul are the same ("Property Dualism"), while others believe that the soul outlives the mind ("Substane Dualism"). Rene Descartes, in his most famous argument, made a thought experiment. He argued that imagination makes anything possible, but imagination is a psychological process and not a logical process. There is the "Barber's paradox", in which a barber shaves only people who shave themselves; this is an imaginable scenario, but lacks logic. However, some would argue that logic itself is a psychological process. Because the body is divisible and the mind is indivisible, Descartes argued, the body and mind are separate substances.
Personal identity[]
There are several criteria for personal identity:
- The Soul Criterion - People remain the same throughout time if they maintain their soul. Favored by very few philosophers.
- The Body Criterion - Common sense informs that persons are their bodies. Normal people adhere to the view that we recognize people by their bodies, while many philosophers disagree.
- Psychological Criteria - A person can only be the same person if there is a psychological continuity, as argued by John Locke. For instance, if a prince and a cobbler's minds were switched, and the guards sought to arrest the prince for a crime, they should arrest the cobbler, as he has the psychological continuity of the Prince.
- Bundle theory - There can be no object without properties, and it is impossible to perceive one.
- Problems with Bodily Resurrection - Cannibalism is problematic, as is population growth. The number of souls cannot remain stable if new bodies constantly come to exist.
Parapsychology[]
Parapsychology is the study of inexplicable psychological cases, such as hidden memories and hypnosis. Parapsychologists explain that some people have extrasensory perception as the result of the Ganzfeld Experiment.