Here is a Christian argument for the existence of God:

1. If God raised Jesus from the dead, then God exists.

2. God raised Jesus from the dead.

Therefore:

3. God exists.

There is no need to make this into a modus tollens, because premise (2) clearly begs the question. The claim that ‘God raised Jesus from the dead’ assumes that there is a God who is available to perform miracles, such as the resurrection of Jesus. But the question at issue is whether God exists, so (2) assumes what needs to be proved.

The above argument can be modified to avoid begging the question:

4. If Jesus rose from the dead, then God exists.

5. Jesus rose from the dead.

Therefore:

3. God exists.

Premise (5) is controversial, but unlike (2) it does not assume that God exists, so (5) does not beg the question, so long as some additional evidence is provided in support of (5). One could make the classic modus tollens skeptical move here:

4. If Jesus rose from the dead, then God exists.

6. It is NOT the case that God exists.

Therefore:

7. It is NOT the case that Jesus rose from the dead.

In other words, one could argue for atheism as an objection to the resurrection of Jesus. However, premise (4) is questionable. Premise (4) assumes that God alone could raise someone from the dead. But there is no good reason to believe this assumption. If we are willing to entertain the hypothesis that there is a bodiless person with supernatural powers, then we ought to be willing to entertain other supernatural hyptotheses as well, such as the existence of fairies, elves, angels, demons, demi-gods, ghosts, witches, wizards, ESP, telekinesis, pyramid power, magic spells, magic potions, curses, fairy dust, etc.

The Bible itself indicates that God is not the only supernatural being. According to the Bible there are thousands of angels and thousands of demons, and millions of spirits of the dead. So, if Jesus really did rise from the dead, at the most this is evidence that some sort of supernatural being or force exists. It could just be that Jesus was a unique human being that had extraordinary supernatural powers, and that there is no God.

So, the above modus tollens argument only works as an ad hominem argument, as an argument that appeals to a Christian belief which we skeptics do not buy into.

But not only is (4) questionable, I would argue that a good case can be made for the opposite of (4), and thus we have the basis for an argument against the existence of God:

8. If Jesus rose from the dead, then God does NOT exist.

5. Jesus rose from the dead.

Therefore:

9. God does NOT exist.

Premise (8) is controversial, so it needs to be supported:

10. If God exists, then God would not raise a false prophet from the dead, nor would God allow a false prophet to be raised from the dead (because that would be a great deception, and God is a perfectly good person, by definition).

11. Jesus was a false prophet (because he promoted prayer to and worship of a false god: Jehovah).

Therefore:

12. If God exists, then God would not raise Jesus from the dead, nor would God allow Jesus to be raised from the dead.

Therefore:

8. If Jesus rose from the dead, then God does NOT exist.

The problem with my skeptical argument is that premise (5) is highly questionable, and would be rejected by most skeptics. But the skeptical argument could be modified into a dilemma:

13. Either Jesus rose from the dead or it is NOT the case that Jesus rose from the dead.

14. If it is NOT the case that Jesus rose from the dead, then Christianity is a false religion.

8. If Jesus rose from the dead, then God does NOT exist.

Therefore:

15. Either Christianity is a false religion or else God does NOT exist.