Hello. This is my first post in this forum and I am exited to be able to discuss important issues with people who care.

The goal of this post is to set the foundation for proving the existence of God. It will, hopefully, prove that there is a first unmoved mover or uncaused cause, who can only be one, who is eternal, and who is all powerful since this being has existence by nature.

First I will go through a few working definitions and disclaimers:

Potentiality is the ability to become something in actuality. It is determinable.
Actually is when a thing really exists in reality in a certain determined way.
So, for example, clay has the potential to be made into a statue, but as clay it is actually clay and is not a statue in act, but only in potential.

"Motion is nothing else than the reduction of something from potentiality to actuality." (St Thomas Summa) Note that Motion is being used in a more broad sense than normal. For instance, water which is boiled is moved from cool to hot. The cool water had the potential to be hot. The fire moved or cause it to be hot, which is to say it became hot in act.

The argument from motion is an à posteriori.

The argument does not state everything which exists is moved or everything which moves something else must have been moved.

Furthermore, the arguments I present don't need to prove everything about God in order to prove something.

I am not trying to prove Christianity or Catholicism in this post, which ultimately cannot be proved with absolute certainty by reason or historical evidence.

Now here is the first way of St. Thomas with modifications:

1. (Premise) It is evident that there is motion which is nothing else than the reduction of something from potentiality to actuality. (Empirical fact)
2. (Premise) Everything which is moved cannot move itself. Potency in one respect cannot actualize itself in the same respect. Something in act must actualize the potency. (Empirical fact and necessary via principle of non contradiction)
3. (Premise) "If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand." Also note that the first mover is primary and not necessarily first temporally in a series. St. Thomas explains elsewhere in the Summa that he thinks the world could be eternal and there could be an infinitely long series of non-subordinated causes. For instance, at least in principle according to Thomas, there could be an infinitely long chain of rail road cars moving, but there would still need to be a locomotive with an engine to move the infinite rail road cars. (Necessary via principle of sufficient reason)
4. (Conclusion) Therefore, since there is motion (1), there must be a first mover who is an unmoved mover (2) and (3).

So what is special about this unmoved mover? Why should we call him God? I won't prove that he he has all of the divine attributes in this post, but I will prove the basis for many of the devine attributes. Namely, that the unmoved mover is pure act and has existence by his own essence or rather, his essence is his existence and vice versa.
Here is my second syllogism:

1. Being presupposes causation/motion. Existence presupposes motion.
2. Things which are contingent have the potential to exist or not to exist.
3. Some things are contingent.
4. Their existence must be actualized by something else with existence.
5. This cannot go on infinitely between beings who needed their existence to be actualized.
6. Therefore a being who has existence in act by nature and who does not need existence to be actualized by another must exist.

Since this being has existence by nature and since a being is in act in so far as it exists in a certain way, the being in 6 must posses act in itself since it possess existence in itself. So, that being is pure act, which is what I call God. It is pure act because it does not have existence in a limited way, but is existence itself. Again, I am not trying to prove that this being has all of the divine attributes.

I suggest reading a few paragraphs from this link to know what a per se ordered casual series is
http://edwardfeser.blogspot.com/2010/08/edwards-on-infinite-causal-serie...

Now, I will present the second way of St. Thomas which proves a first cause:

1. We perceive a series of efficient causes of things in the world.

2. Nothing exists prior to itself.

3. Therefore nothing [in the world of things we perceive] is the efficient cause of itself.

4. If a previous efficient cause does not exist, neither does the thing that results (the effect).

5. Therefore if the first thing in a series does not exist, nothing in the series exists.

6. If the series of efficient causes ordered per se extends ad infinitum into the past, then there would be no things existing now.

7. That is plainly false (i.e., there are things existing now that came about through efficient causes).

8. Therefore efficient causes do not extend ad infinitum in a per se casual series.

9. Therefore it is necessary to admit a first efficient cause.

This syllogism is from this cite with some slight modifications:
http://web.mnstate.edu/gracyk/courses/web%20publishing/aquinasFiveWays_A...

This first cause is uncaused necessarily. It has casual power by its own nature. Therefore, it has existence by nature and therefore you can say that it's essence is its existence.
But why can't there be two or more of these first causes or first movers?
Well, first off, for there to be two of something with some nature there must be some kind of a difference. Otherwise, they would be the same thing. If two things are the same in every possible way, then they are not two but one. Now, the first uncaused cause must be eternal and without beginning in order to have casual power by nature. Again we can say that it's essence is its nature.
If there were two uncaused causes, then they would have the common nature of existence=essence + some difference/accident. But those differences would not exist by there own nature and hence would have to be caused by a first uncaused cause. Therefore, there could not be two or more uncaused causes since differences in two hypothetical first uncaused causes could not be eternal and would have to be caused.

One last point: this being must be all powerful. Power is the ability to do something. To have power one must exist. If one can cause something to exist then he has power to do that. This being has existence and causality by its own nature and by necessity. Therefore, it is power by its own nature and can cause any possible thing to exist. It is therefore all powerful.

Finally, I will make a few closing statements. The being, which I think I have proved, sounds an awful lot like God. But to see how this being has all of the other divine attributes requires much reading and argumentation which I do not have time to present or at least not in one thread. So, I suggest that you read the relevant passages of the Summa Theologica or Summa Contra Gentelis of St. Thomas or a book by Dr. Edward Feser who is a Catholic Thomist philosopher.