Rambam's Argument from Contingency

1) Existence comes in two flavors. An object exists necessarily or contingently.

2) Contingent existence means that it is theoretically possible for it to not exist.

3) Necessary existence is when it is not possible for the object to not exist.

4) When we look at the universe, we see many things (including the universe itself) that exist.

5) Why do they exist?

6) Well, something exists either because a) it must exist (necessarily exists) or b) it was brought into existence by something whose existence we can already explain.

7) As stated in 4, we know things exist.

8) This can only be explained by something that exists necessarily, however far you have to go back.

9) We therefore conclude that Something exists necessarily.

This argument is similar to the first cause argument, but it deals not with temporal contingency, but logical contingency. (This leaves open the door for an eternal universe.)

PS. XGH claims that infinite regress is just as logical to posit as a first cause. However, in fact, if one denies the impossibility of logical infinite regress then one is really denying logic as a formal system. Our whole concept of logic is based on the premise that the world we see around us is founded on cause and effect. This is what gives us permission, given a premise, to infer a conclusion. One who denies this has entered the realm of mysticism and if one has entered mysticism, she is in a very weak position to criticize any form of Emuna whatsoever.