Topics:

• Are there reasons to believe in the existence of God?
• What kind of God (if any) exists?
• What are the implications of God's existence or nonexistence?
• Why do cultures universally believe in gods?
• And of more philosophical importance, do cultures have good reasons to support such beliefs, or are they merely rationalizing--supporting biases and opinions that they want to believe but for which they otherwise have no sound arguments?

This is not to say that theists cannot provide good arguments because they already believe in God's existence. Rather, for them the task of philosophy is to seek out reasons to make belief intelligible: faith seeking understanding.

The Ontological Argument: an a priori argument for the existence of God (that is, an argument showing the existence of God from the meaning of the concept of God as the most perfect or real being, rather than an a posteriori argument based on statements of experienced facts).

• (Anselm's version): 1. Everyone acknowledges that by "God" we mean that being than which nothing greater can be conceived. 2. But a being that exists only in the mind is not as great as a being that exists in the mind as well as in reality. 3. Therefore, God must exist both in the mind and in reality, since a God that existed only in the mind would not be that being than which nothing greater could be conceived.

• (Descartes' version): 1. God is by definition absolutely perfect. 2. It is more perfect for a thing to exist than not to exist (at least this is what people practically believe). 3. Therefore, God must exist.

• Hume's refutation (based on flaws in the logic of the argument): if we can conceive of something, it is not a logical contradiction. If something is conceivable as existing, it can likewise be conceived of as nonexistent (and this applies to God as well). It is always illegitimate to think that from a definition, idea, or statement of meanings that one can make claims about reality (which are always based on observations).

• Kant's refutation (based on flaws in the grammar of the argument): Existence is not a predicate. That is, to say of God that He exists or does not exist does not add or subtract anything from the concept of God; it only affirms that there is something that I think when I use the word "God." To imagine or think of anything presupposes that the thing exists as the object of thought. To imagine or think that the thing exists in no way changes what one thinks: it still is the object of what one is thinking.

• Malcolm's revision: If God does not exist, His nonexistence is logically necessary (that is, His existence is inconceivable). If He does exist, then He must have always and necessarily existed, for He cannot have come into existence because that would mean that He is not eternal and independently perfect. Hence, either the concept of God's existence is logically impossible (self-contradictory) or logically necessary. But it is not self-contradictory, so it must be logically necessary (that is, God exists).

  In other words, if by definition, God is eternal and cannot have come into existence or have been caused to come into existence, then by definition if he exists at all, his existence is part of what he is: that is, his existence is logically necessary. If God does not exist, his not existing must also be part of his very definition, because nothing other than that definition could account for his actually existing or not. But if God's non-existence is part of his definition, then his existence is logically impossible (which would mean that the existence of God would be a contradiction in terms, a logical contradiction). However, we know that there is nothing logically contradictory about a God who exists, so we can rule out the possibility that God does not exist. The only other available option is that he exists, and (as shown above) if he exists he exists necessarily.