Rather than retype a billion things myself I have gone to people with more brains than me on this issue and see what you think.  I am more of theologian than a apologist (one who proves to others outside the faith that the tennets of faith are true).

The following is the theist most common arguments for the existence of God:

Arguments for the Existence of God

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Proofs FOR the Existence of God

While theology may take God's existence as absolutely necessary on the basis of authority, faith, or revelation, many philosophers-and some theologians-have thought it possible to demonstrate by reason that there must be a God.

St. Thomas Aquinas, in the thirteenth century, formulated the famous "five ways" by which God's existence can be demonstrated philosophically:

• 1. The "unmoved mover" argument. We know that there is motion in the world; whatever is in motion is moved by another thing; this other thing also must be moved by something; to avoid an infinite regression, we must posit a "first mover," which is God.
• 2. The "nothing is caused by itself" argument. For example, a table is brought into being by a carpenter, who is caused by his parents. Again, we cannot go on to infinity, so there must be a first cause, which is God.
• 3. The cosmological argument. All physical things, even mountains, boulders, and rivers, come into being and go out of existence, no matter how long they last. Therefore, since time is infinite, there must be some time at which none of these things existed. But if there were nothing at that point in time, how could there be anything at all now, since nothing cannot cause anything? Thus, there must always have been at least one necessary thing that is eternal, which is God.
• 4. Objects in the world have differing degrees of qualities such as goodness. But speaking of more or less goodness makes sense only by comparison with what is the maximum goodness, which is God.
• 5. The teleological argument (argument from design). Things in the world move toward goals, just as the arrow does not move toward its goal except by the archer's directing it. Thus, there must be an intelligent designer who directs all things to their goals, and this is God.

Immanuel Kant rejected not only the ontological argument but the teleological and cosmological arguments as well, based on his theory that reason is too limited to know anything beyond human experience. However, he did argue that religion could be established as presupposed by the workings of morality in the human mind ("practical reason"). God's existence is a necessary presupposition of there being any moral judgments that are objective, that go beyond mere relativistic moral preferences; such judgments require standards external to any human mind-that is, they presume God's mind.

Arguments AGAINST God's Existence

Arguments against God's existence have been given by philosophers, atheists, and agnostics. Some of these arguments find God's existence incompatible with observed facts; some are arguments that God does not exist because the concept of God is incoherent or confused. Others are criticisms of the proofs offered for God's existence.

One of the most influential and powerful "proofs" that there is no God proceeds from "The Problem From Evil." This argument claims that the following three statements cannot all be true: (a) evil exists; (b) God is omnipotent; and (c) God is all-loving. The argument is as follows:

• - if God can prevent evil, but doesn't, then He isn't all-loving.
• - if God intends to prevent evil, but cannot, then He isn't omnipotent.
• - if God both intends to prevent evil and is capable of doing so, then how can evil exist?

Another argument claims that the existence of an all-knowing God is incompatible with the fact of free will-that humans do make choices. If God is omniscient, He must know beforehand exactly what a person will do in a given situation. In that case, a person is not in fact free to do the alternative to what God knows he or she will do, and free will must be an illusion. To take this one step further, if one chooses to commit a sin, how can it then be said that one sinned freely?

Hume provided powerful critiques of the main arguments for God's existence. Against the cosmological argument (Aquinas' third argument), he argued that the idea of a necessarily existing being is absurd. Hume stated, "Whatever we can conceive as existent, we can also conceive as nonexistent." He also asked why the ultimate source of the universe could not be the entire universe itself, eternal and uncaused, without a God?

Hume also criticized the argument from design (Aquinas' fifth argument). In particular, he emphasized that there is no legitimate way we can infer the properties of God as the creator of the world from the qualities of His creation. For instance, Hume questioned how we can be sure that the world was not created by a team; or that this is not one of many attempts at creations, the first few having been botched; or, on the other hand, that our world is not a poor first attempt "of an infant deity who afterwards abandoned it, ashamed of his lame performance."

Arguments for the Existence of God

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The arguments for the existence of God constitute one of the finest attempts of the human mind to break out of the world and go beyond the sensible or phenomenal realm of experience.

Certainly the question of God's existence is the most important question of human philosophy. It affects the whole tenor of human life, whether man is regarded as the supreme being in the universe or whether it is believed that man has a superior being that he must love and obey, or perhaps defy.

There are three ways one can argue for the existence of God.

• First, the a priori approach argues from a conception of God as a being so perfect that his nonexistence is inconceivable.
• Second, the a posteriori approach gives evidence from the world, from the observable, empirical universe, insisting that God is necessary to explain certain features of the cosmos.
• Third, the existential approach asserts direct experience of God by way of personal revelation. This approach is not really an argument in the usual sense, because one does not usually argue for something that can be directly experienced.

The A Priori Approach

This approach is the heart of the famous ontological argument, devised by Anselm of Canterbury though adumbrated earlier in the system of Augustine. This argument begins with a special definition of God as infinite, perfect, and necessary.

Anselm said that God cannot be conceived in any way other than "a being than which nothing greater can be conceived." Even the fool knows what he means by "God" when he asserts, "There is no God" (Ps. 14:1). But if the most perfect being existed only in thought and not in reality, then it would not really be the most perfect being, for the one that existed in reality would be more perfect. Therefore, concludes Anselm, "no one who understands what God is, can conceive that God does not exist." In short, it would be self contradictory to say, "I can think of a perfect being that doesn't exist," because existence would have to be a part of perfection. One would be saying, "I can conceive of something greater than that which nothing greater can be conceived", which is absurd.

The ontological argument has had a long and stormy history. It has appealed to some of the finest minds in Western history, usually mathematicians like Descartes, Spinoza, and Leibniz. However, it fails to persuade most people, who seem to harbor the same suspicion as Kant that "the unconditioned necessity of a judgment does not form the absolute necessity of a thing." That is, perfection may not be a true predicate and thus a proposition can be logically necessary without being true in fact.

The A Posteriori Approach

Popular mentality seems to appreciate the a posteriori approach better. The ontological argument can be made without ever appealing to sensation, but the cosmological and teleological arguments require a careful look at the world. The former focuses on the cause, while the latter stresses the design of the universe.

The Cosmological Argument

This has more than one form. The earliest occurs in Plato (Laws, Book X) and Aristotle (Metaphysics, Book VIII) and stresses the need to explain the cause of motion. Assuming that rest is natural and motion is unnatural, these thinkers arrived at God as the necessary Prime Mover of all things. Thomas Aquinas used motion as his first proof in the Summa Theologica (Q.2, Art.3). Everything that moves has to be moved by another thing. But this chain of movers cannot go on to infinity, a key assumption, because there would then be no first mover and thus no other mover. We must arrive, therefore, at a first mover, Aquinas concludes, "and this everyone understands to be God."

This argument from motion is not nearly as cogent for our scientific generation because we take motion to be natural and rest to be unnatural, as the principle of inertia states. Many philosophers insist that the notion of an infinite series of movers is not at all impossible or contradictory.

The most interesting, and persuasive, form of the cosmological argument is Aquinas's "third way," the argument from contingency. Its strength derives from the way it employs both permanence and change. Epicurus stated the metaphysical problem centuries ago: "Something obviously exists now, and something never sprang from nothing." Being, therefore, must have been without beginning. An Eternal Something must be admitted by all, theist, atheist, and agnostic.

But the physical universe could not be this Eternal Something because it is obviously contingent, mutable, subject to decay. How could a decomposing entity explain itself to all eternity? If every present contingent thing / event depends on a previous contingent thing / event and so on ad infinitum, then this does not provide an adequate explanation of anything.

Hence, for there to be anything at all contingent in the universe, there must be at least one thing that is not contingent, something that is necessary throughout all change and self established. In this case "necessary" does not apply to a proposition but to a thing, and it means infinite, eternal, everlasting, self caused, self existent.

It is not enough to say that infinite time will solve the problem of contingent being. No matter how much time you have, dependent being is still dependent on something. Everything contingent within the span of infinity will, at some particular moment, not exist. But if there was a moment when nothing existed, then nothing would exist now.

The choice is simple: one chooses either a self existent God or a self existent universe, and the universe is not behaving as if it is self existent. In fact, according to the second law of thermodynamics, the universe is running down like a clock or, better, cooling off like a giant stove. Energy is constantly being diffused or dissipated, that is, progressively distributed throughout the universe. If this process goes on for a few billion more years, and scientists have never observed a restoration of dissipated energy, then the result will be a state of thermal equilibrium, a "heat death," a random degradation of energy throughout the entire cosmos and hence the stagnation of all physical activity.

Naturalists from Lucretius to Sagan have felt that we need not postulate God as long as nature can be considered a self explanatory entity for all eternity. But it is difficult to hold this doctrine if the second law [of thermodynamics] is true and entropy is irreversible. If the cosmos is running down or cooling off, then it could not have been running and cooling forever. It must have had a beginning.

A popular retort to the cosmological argument is to ask, "If God made the universe, then who made God?" If one insists that the world had a cause, must one not also insist that God had a cause? No, because if God is a necessary being, this is established if one accepts the proof, then it is unnecessary to inquire into his origins. It would be like asking, "Who made the unmakable being?" or "Who caused the uncausable being?"

More serious is the objection that the proof is based on an uncritical acceptance of the "principle of sufficient reason," the notion that every event / effect has a cause. If this principle is denied, even if it is denied in metaphysics, the cosmological argument is defanged. Hume argued that causation is a psychological, not a metaphysical, principle, one whose origins lay in the human propensity to assume necessary connections between events when all we really see is contiguity and succession. Kant seconded Hume by arguing that causation is a category built into our minds as one of the many ways in which we order our experience. Sartre felt that the universe was "gratuitous." Bertrand Russell claimed that the question of origins was tangled in meaningless verbiage and that we must be content to declare that the universe is "just there and that's all."

One does not prove the principle of causality easily. It is one of those foundational assumptions that is made in building a world view. It can be pointed out, however, that if we jettison the idea of sufficient reason, we will destroy not only metaphysics but science as well. When one attacks causality, one attacks much of knowledge per se, for without this principle the rational connection in most of our learning falls to pieces. Surely it is not irrational to inquire into the cause of the entire universe.

The Teleological or Design Argument

This is one of the oldest and most popular and intelligible of the theistic proofs. It suggests that there is a definite analogy between the order and regularity of the cosmos and a product of human ingenuity. Voltaire put it in rather simplistic terms: "If a watch proves the existence of a watchmaker but the universe does not prove the existence of a great Architect, then I consent to be called a fool."

No one can deny the universe seems to be designed; instances of purposive ordering are all around us. Almost anywhere can be found features of being that show the universe to be basically friendly to life, mind, personality, and values. Life itself is a cosmic function, that is, a very complex arrangement of things both terrestrial and extraterrestrial must obtain before life can subsist. The earth must be just the right size, its rotation must be within certain limits, its tilt must be correct to cause the seasons, its land - water ratio must be a delicate balance. Our biological structure is very fragile. A little too much heat or cold and we die. We need light, but not too much ultraviolet. We need heat, but not too much infrared. We live just beneath an airscreen shielding us from millions of missiles every day. We live just ten miles above a rock screen that shields us from the terrible heat under our feet. Who created all these screens and shields that make our earthly existence possible?

Once again we are faced with a choice. Either the universe was designed or it developed all these features by chance. The cosmos is either a plan or an accident!

Most people have an innate repugnance to the notion of chance because it contradicts the way we ordinarily explain things. Chance is not an explanation but an abandonment of explanation. When a scientist explains an immediate event, he operates on the assumption that this is a regular universe where everything occurs as a result of the orderly procession of cause and effect. Yet when the naturalist comes to metaphysics, to the origin of the entire cosmos, he abandons the principle of sufficient reason and assumes that the cause of everything is an unthinkable causelessness, chance, or fate.

Suppose you were standing facing a target and you saw an arrow fired from behind you hit the bull's eye. Then you saw nine more arrows fired in rapid succession all hitting the same bull's eye. The aim is so accurate that each arrow splits the previous arrow as it hits. Now an arrow shot into the air is subject to many contrary and discordant processes, gravity, air pressure, and wind. When ten arrows reach the bull's eye, does this not rule out the possibility of mere chance? Would you not say that this was the result of an expert archer? Is this parable not analogous to our universe?

It is objected that the design argument, even if valid, does not prove a creator but only an architect, and even then only an architect intelligent enough to produce the known universe, not necessarily an omniscient being. This objection is correct. We must not try to prove more than the evidence will allow. We will not get the 100 percent Yahweh of the Bible from any evidence of natural theology. However, this universe of ours is so vast and wonderful we can safely conclude that its designer would be worthy of our worship and devotion.

Many object that the theory of evolution takes most of the wind out of the design argument. Evolution shows that the marvelous design in living organisms came about by slow adaptation to the environment, not by intelligent creation. This is a false claim. Even if admitted, evolution only introduces a longer time frame into the question of design. Proving that watches came from a completely automated factory with no human intervention would not make us give up interest in a designer, for if we thought a watch was wonderful, what must we think of a factory that produces watches? Would it not suggest a designer just as forcefully? Religious people have been overly frightened by the theory of evolution.

Even the great critics of natural theology, Hume and Kant, betrayed an admiration for the teleological argument. Hume granted it a certain limited validity. Kant went even further: "This proof will always deserve to be treated with respect. It is the oldest, the clearest and most in conformity with human reason . . . We have nothing to say against the reasonableness and utility of this line of argument, but wish, on the contrary, to commend and encourage it."

The Moral Argument

This is the most recent of the theistic proofs. The first major philosopher to use it was Kant, who felt that the traditional proofs were defective. Kant held that the existence of God and the immortality of the soul were matters of faith, not ordinary speculative reason, which, he claimed, is limited to sensation.

Kant reasoned that the moral law commands us to seek the summum bonum (highest good), with perfect happiness as a logical result. But a problem arises when we contemplate the unpleasant fact that "there is not the slightest ground in the moral law for a necessary connexion between morality and proportionate happiness in a being that belongs to the world as a part of it." The only postulate, therefore, that will make sense of man's moral experience is "the existence of a cause of all nature, distinct from nature itself," i.e., a God who will properly reward moral endeavor in another world. In a godless universe man's deepest experience would be a cruel enigma.

In his Rumor of Angels, Peter Berger gives an interesting negative version of the moral argument, which he calls "the argument from damnation." Our apodictic moral condemnation of such immoral men as Adolf Eichmann seems to transcend tastes and mores; it seems to demand a condemnation of supernatural dimensions.

Some deeds are not only evil but monstrously evil; they appear immune to any kind of moral relativizing. In making such high voltage moral judgments, as when we condemn slavery and genocide, we point to a transcendent realm of moral absolutes. Otherwise, all our moralizing is pointless and groundless. A "preaching relativist" is one of the most comical of self contradictions.

Most modern thinkers who use the moral argument continue Kant's thesis that God is a necessary postulate to explain moral experience. Kant thought the moral law could be established by reason, but he called in God to guarantee the reward for virtue. Modern thinkers do not use God so much for the reward as for providing a ground for the moral law in the first place.

The moral argument starts with the simple fact of ethical experience. The pressure to do one's duty can be felt as strongly as the pressure of an empirical object. Who or what is causing this pressure? It is not enough to say that we are conditioned by society to feel those pressures. Some of the greatest moralists in history have acquired their fame precisely because they criticized the moral failings of their group, tribe, class, race, or nation. If social subjectivism is the explanation of moral motivation, then we have no right to criticize slavery or genocide or anything!

Evolutionists attack the moral argument by insisting that all morality is merely a long development from animal instincts. Men gradually work out their ethical systems by living together in social communities. But this objection is a two edged sword: if it kills morality, it also kills reason and the scientific method. The evolutionist believes that the human intellect developed from the physical brain of the primates, yet he assumes that the intellect is trustworthy. If the mind is entitled to trust, though evolved from the lower forms, why not the moral nature also?

Many people will go part way and accept moral objectivism, but they want to stop with a transcendent realm of impersonal moral absolutes. They deny that one must believe in a Person, Mind, or Lawgiver. This seems reductive. It is difficult to imagine an "impersonal mind." How could a thing make us feel duty bound to be kind, helpful, truthful, and loving? We should press on, all the way to a Person, God, the Lawgiver. Only then is the moral experience adequately explained.

The Question of Validity

How valid are all these theistic proofs? This question raises issues in a number of fields: logic, metaphysics, physics, and theory of knowledge. Some thinkers like Aquinas feel that the proofs reach the level of demonstration. Others like Hume say that we should just suspend judgment and remain skeptics. Still others like Pascal and Kant reject the traditional proofs but offer instead practical grounds or reasons for accepting God's existence. Pascal's famous wager is an appeal to pragmatism; it makes sense, in view of the eternal consequences, to bet on the existence of God.

Paul seems to demand a high view of the theistic proofs when he says that the unbelievers are "without excuse." "What can be known about God is plain to them, because God has shown it to them. Ever since the creation of the world his invisible nature, namely his eternal power and deity, has been clearly perceived in the things that have been made" (Rom. 1:19 - 20).

Paul was not necessarily affirming that the arguments are deductive, analytical, or demonstrative. If someone rejected a proposition of high probability, we could still say that he was "without excuse." The arguments, in their cumulative effect, make a very strong case for the existence of God, but they are not logically inexorable or rationally inevitable. If we define proof as probable occurrence based on empirically produced experiences and subject to the test of reasonable judgment, then we can say the arguments prove the existence of God.

If God truly exists, then we are dealing with a factual proposition, and what we really want when we ask for proof of a factual proposition is not a demonstration of its logical impossibility but a degree of evidence that will exclude reasonable doubt. Something can be so probable that it excludes reasonable doubt without being deductive or analytical or demonstrative or logically inevitable. We feel that the theistic proofs, excluding the ontological argument, fall into this category.

Natural theology, however, can never establish the existence of the biblical God. These proofs may make one a deist, but only revelation will make one a Christian. Reason operating without revelation always turns up with a deity different from Yahweh, the Father of Our Lord Jesus Christ. One can confirm this easily by comparing Yahweh with the deities of Aristotle, Spinoza, Voltaire, and Thomas Paine.

A J Hoover
(Elwell Evangelical Dictionary)

Bibliography
J Baillie, Our Knowledge of God; D Burrill, The Cosmological Argument; G H Clark, A Christian View of Men and Things; R E D Clark, The Universe: Plan or Accident? H H Farmer, Towards Belief in God; R Hazelton, On Proving God; J Hick, The Existence of God; D Hicks, The Philosophical Basis of Theism; A J Hoover, The Case for Christian Theism; S Jaki, The Road of Science and the Ways to God; C E M Joad, God and Evil; J Maritain, Approaches to God; E L Mascall, The Openness of Being; G Mavrodes, The Rationality of Belief in God; A Plantinga, ed., The Ontological Argument; R C Sproul, If There Is a God, Why Are There Atheists? A E Taylor, Does God Exist?

I hope this will get discussion rolling at least on the subject at hand. 

Scientist would never make such a definitive statement as you make -- the sun has burned out three times -- how would they know were they there?  It is guess work by them.  No theory of the origin of the universe can be scientifically proven, period.  Science is experimentation and observation -- the origin of the universe is no longer available to do either to.  Yes, include creationsim in that too.  Why should I trust the scientist?  Is he not capaable of error like me?  If so could his observations be mearly opinion or a best guess?  Sounds like it to me -- they always seem to be guessing and then changing their mind later.  I would not put my 'faith' in science a deeply as you do. 

How do you say the universe has no design to it?  Give me an example of pure random chaos not govened by law but only purely chance and I will become an athiest.  I have put that challenge out before, everyone has failed.     

"Scientist would never make such a definitive statement as you make -- the sun has burned out three times -- how would they know were they there?  It is guess work by them.  No theory of the origin of the universe can be scientifically proven, period.  Science is experimentation and observation -- the origin of the universe is no longer available to do either to.  Yes, include creationsim in that too.  Why should I trust the scientist?  Is he not capaable of error like me?  If so could his observations be mearly opinion or a best guess?  Sounds like it to me -- they always seem to be guessing and then changing their mind later.  I would not put my 'faith' in science a deeply as you do. 

How do you say the universe has no design to it?  Give me an example of pure random chaos not govened by law but only purely chance and I will become an athiest.  I have put that challenge out before, everyone has failed. "  

While it is a theory by scientist,  to me it has more proof to it since they explained the reasons for thinking that way and how it happens. It sounds better then poof there was a god, poof there was earth and poof we got humans in all there glory.

The creationist / evolutionist argument is, I believe, archaic.  Only some Fundamentalist Christians still insist in arguing it (and sadly there are a lot of these Fundamentalist Christians.)  For a lot of Christian denominations, especially more traditional ones (such as those with at least a few centuries of history, like the Catholic Church,) evolution is never quit a bother.  The reason is that there are many ways to understand the Genesis account.  If I'm not mistaken, St. Augustine, regarded as a doctor of the Church, suggested that the seven "days" be regarded metaphorically, and this was way before evolution theories were formed.  Evolution isn't an argument against the Bible at all.

Yes, I think people who counter religious arguments always tend to fall into the trap of intertextuality and draw in other assumed attributes about god.

"We know that there is motion in the world; whatever is in motion is moved by another thing; this other thing also must be moved by something; to avoid an infinite regression, we must posit a "first mover," which is God. " Aquinas

Clearly what Aquinas is saying is God was simply a name for the initial proton that sparked the Big Bang and ceased to exist 1,000,000,000,000th of a micro second later.