Notes

Arguments for and against the existence of God have been proposed by philosophers, theologians, scientists, and others for thousands of years. In philosophical terms, such arguments involve primarily the disciplines of epistemology (the nature and scope of knowledge) and ontology (study of the nature of being, existence, or reality) and also the theory of value, since concepts of perfection are connected to notions of God. A wide variety of arguments exist which can be categorized as metaphysical, logical, empirical, or subjective. The existence of God is subject to lively debate in philosophy,[1] the philosophy of religion, and popular culture.
The Western tradition of philosophical discussion of the existence of God began with Plato and Aristotle, who made arguments that would now be categorized as cosmological. Other arguments for the existence of God have been proposed by St. Anselm, who formulated the first ontological argument; Ibn Rushd (Averroes) and Aquinas, who presented their own versions of the cosmological argument (the kalam argument and the first way, respectively); Descartes, who said that the existence of a benevolent God was logically necessary for the evidence of the senses to be meaningful; and Immanuel Kant, who argued that the existence of God can be deduced from the existence of good.

Definition of God
In Classical theism, God is characterized as the metaphysically ultimate being (the first, timeless, absolutely simple, and sovereign being, who is devoid of any anthropomorphic qualities), in distinction to other conceptions such as Theistic Personalism, Open Theism, and Process Theism. Despite extensive writing on the nature of God, these classical theists did not believe that God could be defined. They believed that it would contradict the transcendent nature of God for mere humans to define him. Robert Barron explains by analogy that it seems impossible for a two-dimensional object to conceive of three-dimensional humans.[4]
By contrast, much of Eastern religious thought (chiefly pantheism) posits God as a force contained in every imaginable phenomenon. For example, Baruch Spinoza and his followers use the term God in a particular philosophical sense to mean the essential substance/principles of nature.
In modern Western societies, the concept of God typically entails a monotheistic, supreme, ultimate, and personal being, as found in the Islamic, Christian and Hebrew traditions. In monotheisms outside the Abrahamic traditions, the existence of God is discussed in similar terms.
In the Advaita Vedanta school of Hinduism, reality is ultimately seen as a single, qualityless, changeless nirguna Brahman. Advaitin philosophy introduces the concept of saguna Brahman or Ishvara as a way of talking about Brahman to people. Ishvara, in turn, is ascribed such qualities as omniscience, omnipotence, and benevolence.

Traditional "proofs" of God's Existence

1) The argument from Design.

If you found a clock and examined the mechanism within it, you would probably think that this intricate mechanism was not the outcome of mere chance, that it had been designed.

Now look at the universe; is it possible that such an intricate mechanism, from the orbits of planets round the sun to the cells in your fingernails could all have happened by chance? Surely, this enormously complex mechanism has been designed, and the being that designed it must be God.

2) The ontological argument

God is the perfect being. As He is most perfect, He must have all perfections. If God lacked existence He would not be perfect, as He is perfect he must exist.

3) The cosmological argument (God as "First cause")

Everything that exists has a cause. However, there must at some time have been a cause prior to all other causes. This 'prime mover' or first cause is necessary to explain existence. This first cause is God.

Pascal's Wager

The French mathematician Blaise Pascal (1623-62) put forward an argument that would appeal to agnostics. (An agnostic is someone who believes that it is impossible to prove God's existence.)

His argument goes something like this: God either exists or he does not. If we believe in God and he exists, we will be rewarded with eternal bliss in heaven. If we believe in God and he does not exist then at worst all we have forgone is a few sinful pleasures.

If we do not believe in God and he does exist we may enjoy a few sinful pleasures, but we may face eternal damnation. If we do not believe in God and he does not exist then our sins will not be punished.

Would any rational gambler think that the experience of a few sinful pleasures is worth the risk of eternal damnation?

Kant

Kant attempted to show how philosophy could prove the existence of God. Unfortunately, for him his previous work showed that we could not know reality directly as thing-in-itself. What is real in itself is beyond our experience. Even if God exists, we can not know God as he really is.

For Kant the Christian could have faith in God, and this faith would be consonant with reason and the categorical imperative. Given that human beings have the autonomy to create moral values, it would not be irrational to believe in a God who gives purpose to the moral realm.

Hegel

Hegel thought that the God of religion was an intuition of Absolute Spirit or Geist. Hegel's Geist is not like the transcendent (outside of our consciousness) God of traditional Christianity. For Hegel God is immanent and when we have understood that history is the process of Geist coming to know itself it appears that we are all part of Geist, or God.

Søren Kierkegaard

Søren Kierkegaard (1813-1855) agreed with Kant that the existence of God could not be proven by reason. However Kierkegaard did not think that it was rational to believe in God, rather one should have faith in God even if this seems to reason to be absurd. To put it another way reason has no place in faith. God is beyond reason.
Kierkegaard is regarded as the first existentialist.

Conclusion

Of course, these proofs have their share of proponents and opponents. The proofs do not definitively prove the existence of God because they can be argued. Even the greatest truth can be masked behind a veil of innocent ignorance or blindness of pride. It is faith that provides the bedrock for belief in God and the cornerstone for ultimate happiness