Now that Jared has listed fallacies in informal logic it might be useful to apply them to some of the more commonly used religious apologetics.

I'll start us off with the argument from apparent design or teleological argument. We'll start with Aquinas.

"The Teleological argument is founded on Aquinas's fifth way:

1. All natural occurrences show evidence of design
2. This suggests that there is a being that directs all things
3. Things that lack knowledge cannot achieve anything unless directed by a thing with knowledge
4. There is therefore an intelligent being that directs everyone towards a purpose
5. For Aquinas, this being is God

1. So straight away we see in 1 the common logical fallacy of begging the question, by asserting the very thing he's arguing for in the argument, namely design in nature.
2. Here he's using argumentum ad ignorantiam, the fact there is an inexplicable appearance of design he couldn't explain has been used to imply a being. Note he was wholly unaware that complexity of all living things is fully and naturally explained by evolution.
3. Begging the question again, since has is asserting in his argument the very thing he is arguing for.
4. The conclusion of course is fallacious because the premises it's based on are demonstrably irrational. However we should also not the way the conclusion simply assumes that complexity and knowledge indicates purpose as well as design. Again this is begging the question.
5. Nothing needs to be said here as this is begging the question as it is pure assumption of the thing he's arguing for in his argument.

I might get shot down for using antiquated apologetics here, but please bear in mind that Aquinas's 5 ways was cited by two different theists in the EVIDENCE thread I started, as "objective evidence" for the existence of a deity.

The best example of a straw man argument is Willaim Lane Craig insisting atheists 'must' believe something can come from nothing.

It's usually followed up by a false dichotomy where he insists explanations for the origins of the universe are limited to either a deity or the above straw man argument. Since we dont know how the universe originated he can't know what our options are or how many there are, that's axiomatic.

Also note Craig's inclusion of a deity as one possibility without a shred of evidence and again in an argument for that deity, so begging the question again.

One more common logical fallacy is post hoc ergo propter hoc, or after this therefore because of this. Where causation is assigned to a preceding event without evidence.

This is most commonly used to fallaciously validate prayer. Where a prayer is made and the result is favourable and the prayer is cited as the cause without any evidence.

This often uses the sharpshooter fallacy as well, its a selection bias where only the "successful" prayers are cited after the event, and the failures are ignored.

Jared Alesi,

Your list of fallacies was outstanding--and useful! Hope you don't mind if I do some heavy-duty editing to pull it all together, including contributions from Sheldon, Irving Copi ("Introduction to Logic" 7th edition) and other sources. I hope to make it as clear and useful as possible rather than technical. A comprehensive list would have to cover way too many examples, but there are no doubt a few popular items that I missed that should be included--a job for later editing.

Ad hoc (For this purpose only): The fallacy of advancing, without evidence, a claim designed solely to save an argument from some criticism. (A loophole is appealed to without justification. Example: The story of Peter's denial of Jesus has the campfire in two different places--a contradiction! No it isn't, says the Bible-believer, because there were really two campfires! But, there is no biblical evidence for that and, indeed, the scenario becomes positively awkward.)

Appeal to authority: A fallacious argument asserting that a claim is correct because an authority figure supports it. (Example: Dr. so and so has written a thick book filled with equations that proves that the sun goes around the earth. So, the Earth doesn't go around the sun! Uh, maybe we should actually take a close look at those arguments! Quoting authority figures simply bypasses the reasoning process, and any debate is all about facts and reasoning. However, quoting recognized authorities can be a good way to show where the scientific community stands on an issue. That does carry a lot of weight even though it is not an argument per se. It can also be a good way to present professional explanations of concepts and terms used by experts in some field.

Appeal to Ignorance: The fallacy of claiming that if the opposition can't prove its case then our case is true by default. (Perhaps more evidence will come in and the opposition will prove its case! The opposition may be incompetent. Both cases may be wrong! Example: If Johnny can't prove he didn't harass Jane, then he must be guilty!)

Appeal to popularity: An attempt to win an argument by noting that almost everyone supports it. (Way back in the bad, old days it was a great way to prove that the world was flat!)

Appeal to Tradition: An appeal claiming that an action or conclusion in accordance with long-established customs is best. (Example: Women should be good housewives because that has always been the natural order of things.)

Argument from Ignorance (Argumentum ad Ignorantiam): The fallacy of advancing a claim on the basis that no one has proven it false. (Examples: Prove that God doesn't exist, says the believer, or else admit that I have a good case. Prove that Zeus doesn't exist or I have a good case! On this basis we could make a good case for all kinds of things, including the Great, Green Spider who lives in the clouds of Jupiter and rules over the Solar System. Obviously, this is no way to reason.)

Argument from Memory: The fallacy of relaying personal memories as factual. (Studies have shown that memory is influenced by a huge number of factors, is reworked, and is therefore unreliable. Memory is anything but a securely stored video tape.)

Argument from Personal Incredulity: The claim that if an idea makes no sense to us then it must be nonsense. (Example: I can't even imagine how the blind forces of evolution could have possibly created that complex factory called a "leaf." The idea of evolution is just so absurd! But, nature is hardly required to accommodate educated (let alone uneducated) opinions as to what is reasonable. The universe and mathematics is full of deep subtleties that defy common sense.)

Begging the Question (petitio principii): The fallacy of borrowing from the conclusion in order to reach the conclusion, or assuming that which must be proved (the conclusion or part of it). (Example: Natural laws don't apply to God's superpowers and are, therefore, not an argument against God. God's supernatural powers, and therefore God, are assumed to exist. The conclusion is that God's existence is not threatened by natural law. Of course God's existence is not threatened by natural law--or anything else--if we start by assuming that God exists! The real question is whether a being with superpowers is a reasonable conclusion based on the data (natural laws). Often Begging the Question and Circular Reasoning are used synonymously.)

Circular Reasoning: "A" proves "B" and "B" proves "A". (A perfect circle of reasoning going nowhere! Example: The Bible proves that God exists. How do we know that the Bible is right? God wrote the Bible! But "B" is our conclusion, and we cannot use it to support "A"--thereby using "B" to prove itself! Often Circular Reasoning is just another name for Begging the Question, but I like to think of Circular Reasoning as a special case where the conclusion is used whole hog to prove itself.)

Equivocation: The fallacy of equating different definitions of a word throughout an argument to support the conclusion. (Example: A creationist quotes a famous scientist who refers to biological evolution as a theory. "See," the creationist cries, "evolution is merely a theory and nothing more!" The conclusion is that evolution is bunk, a conclusion reached by applying the common definition of "theory" (guesswork or half-baked) to the scientific definition (an idea that has been well tested, explains a whole bunch of related data, is fruitful in generating further research, and that fits in well with other theories). Dishonest creationists count on the fact that most people are woefully short on science and probably don't know the difference.)

False Dichotomy: The fallacy of limiting the outcomes to "A" and "B," arguing that "A" is false, therefore "B" must be true. (Example: Either life arose by evolution or by a creator, God. Creationists then "refute" evolution. Therefore, God must exist! Overlooked, for instance, is the logical possibility that some other natural process might have gotten life started, or that a committee of gods got it started and later died.)

No true Scotsman: The fallacy of defending an accepted, universal generalization from harsh counterexamples by simply switching definitions. (Example: Real Christians would never commit the gross, horrid crimes carried out by the medieval officials of the Church, so those people were not true Christians. Thus, you can't impugn Christianity on their account. In one stroke all bad Christians have been defined out of existence! Christians are normally defined as people subscribing to the doctrine that Jesus was crucified, resurrected, and offered eternal salvation to those who believe in him. Suddenly, the definition gets changed to eliminate all bad Christians!)

Non Sequitur (Argumentum non sequitur): A conclusion that bears no logical relationship to the argument. ("Non sequitur" often gets applied to conclusions whose support bears little or no resemblance to rational arguments.)

Post hoc ergo propter hoc (after this, therefore because of this): If "B" follows "A," then look to "A" as the cause of "B." (Example: Seven kids came down with a serious illness after getting their vaccination shots. Therefore, the vaccination program should be immediately terminated. But, what if those kids lived in five different states and that seven million kids got their shots without any problems? Might we be dealing with other, random causes that bear no relationship to the vaccination program? How many people have a serious auto accident within three weeks of buying a shiny, red car? I suspect we could find at least seven people if we really plowed the data. Should we conclude that buying a shiny, red car is dangerous to your health? Day always follows night; should we conclude that night is the cause of day?)

Slippery Slope: The fallacy of claiming without probable cause that the triggering of one event will trigger a chain of events, the last one being clearly unacceptable. Therefore, the first event should be avoided. (If any of the links are dubious, or if the chain as a whole is unlikely, then the conclusion does not follow.)

Special pleading: Arguing, without proper justification, that the usual rules be lifted for a particular case. (Example: An administrator asks a professor to pass Sayeed even though he failed his math class. "Jack," the administrator pleads, "They will crucify him back in Saudi Arabia if he returns with an "F" and he is a really nice kid. Besides, Saudi Arabia may fund one of our programs and I don't want any problems!" Such arguments, however, are irrelevant with respect to the rules for assigning grades. Accepting such an argument may be a wise choice, but it can never be a logically reasoned conclusion.)

Straw man argument: An attempt to beat the opposition by attacking a much softer, false version of their argument. (Example: Because it deals with blind chance, evolution is no more probable than a tornado sweeping through a junkyard and producing an airplane. But, a lot more than random chance is involved!)