I affirm the position that it is intrinsically impossible for a God to exist.
Contention One: Cause
The laws of conservation of matter and energy clearly state that is impossible for matter and energy to be created from nothing or destroyed into nothing.  This of course means that anything currently existing within space-time must be composed of matter from something else, or converted from other energy. Now, since my definition of God has not been contested, we will be using it, including the part where we define God as having created the universe. The big bang, or any sort of beginning phenomena you care to imagine, would obviously require some type of energy. So God is a being that uses some kind of energy. Again, as we already know, energy does not come from nowhere. Obviously, since the only thing that could have come from nothing is nothing itself, we know that God is synonymous with nothing, or nonexistence. So God is intrinsically impossible.
Contention Two: Omnipotence
Omnipotence has been defined as the ability to do literally everything, as this is even borne out by its roots, omni (all) potence (capability).  So we know that under the currently used and currently uncontested definition of God, God has teh ability to do anything. What this entails is a long string of paradoxes. For example, if God can do anything, then God must be able to think of something that He can't do. In which case, He wouldn't be able to do it, and wouldn't be omnipotent. God would have to be able to create a rock that weighed so much that he couldn't move it. If he can't create the rock, He isn't omnipotent. If he can create the rock, then He can't move it and isn't omnipotent. God would have to be able to create another omnipotent God that could beat Him in an armwrestle. Which would mean that since one of the two Gods couldn't beat the other in an armwrestle, one of them wouldn't be omnipotent. So omnipotence itself is intrinsically impossible, and so under our current and uncontested definition, God is intrinsically impossible.
Contention Three: Omniscience
Omniscience is defined as knowing everything that can be known or having infinite knowledge. But knowing everything isn't really as testable as is needed. Firstly, how would a being know that they are omniscient? Well of course they know, after all, they know everything, including their own omniscience. Right? No, that's circular reasoning. Additionally, the being might think they know everything, and could be wrong. For example, if a God knew infinitely many things except one, say that there are aliens in Andromeda, then they wouldn't know that they didn't know there were aliens in Andromeda. And so they would go along thinking they knew everything and in reality not. In fact, the God would have an infinite number of things they didn't know, because they wouldn't know about the aliens, wouldn't know that they didn't know about the aliens, wouldn't know that they didn't know that they didn't know baout the aliens, etc. Which brings me to another point. What is knowledge? Is it a simple fact? If so, then even if you list off everything that God knows in an infinitely long list, you could still create a second list which just adds "God knows this:" in front of everything on the first list, creating a new list of things God doesn't know just as long as the first.
Contention Four: Omniscience/Omnipotence
So assume the following scenario. Some engineers get together and start designing a skyscraper. So God sees this (because he is omnipresent) and says to himself "I know that when the skyscraper is finished, I will have to chop it in half with a meteor." So ten years later the skyscraper is done. So God says to himself "Time to destroy it with meteors." Now God can do one of two things: destroy it with meteors, or not destroy it with meteors. If he decides that he will destroy it, then he was right when he said he knew what he was going to do. However, this means that God cannot not destroy the skyscraper. This refutes the fact of his own omnipotence. And after He destroys the skyscraper, he can't change his mind and undo it, because then he would be wrong when He said he knew he would destroy it. So what if He doesn't destroy it? Then this means that when He said that he knew He was going to destroy it that He was wrong, meaning that God isn't omniscient. So it is intrinsically impossible to be omnipotent and omniscient, meaning it is intrinsically impossible for a God to exist.
These are my four main reasons why I believe that it is intrinsically impossible for a God as we have defined to exist.
Contention 1: Cause
Pro claims that the laws of conservation of matter and energy clearly state that is impossible for matter and energy to be created from nothing or destroyed into nothing, and God would have to create the universe from nothing, therefore, God is impossible. This is just a bad argument for a number of reasons:
(i) It misconstrues the first law of thermodynamics
(ii) It assumes that states of affairs describable by the first law of thermodynamics existed prior to the universe
(iii) It neglects the possibility of a zero energy universe
(iv) It does not deal specifically with an intrinsic contradiction of God
(i): The first law of thermodynamics only assumes that the total net energy of a closed system can never change. Yes, it is inferred from this that energy cannot be created or destroyed, but that is not a logically necessary consequent as many definitions forget about a zero energy universe; as I will explain.
(ii): If states of affairs describable by the first law of thermodynamics begin at the same time as all the energy, then energy conservation is never violated for as long as these states of affairs where energy conservation holds exist. This idea that the creation of the universe violates energy conservation assumes that energy conservation holds prior to the universe. Why think such a thing?
(iii): Lets assume that the my opponent is correct, and that states of affairs describable by energy conservation exist explanatorily prior to the first bit of energy created. There is still a way around a violation of the first law of thermodynamics. As esteemed physicist Alexander Vilenkin explains:
"[T]he universe could have originated spontaneously out of 'nothing'. This sounds like a very strange proposition for a physicist to make because we know that there are conservation laws... energy is conserved. So, usually, this means that if you have nothing you cannot have something because that takes energy. However, it turns out that if you have a closed universe where the space closes in on itself...the gravitational energy which is always negative exactly compensates the positive energy of matter. So, the energy of a closed universe is always zero, and then nothing prevents this universe from being spontaneously created." - Alexander Vilenkin
If you have 0 energy, you can get energy, as long as you have enough negative energy to balance it out so it always equals zero (the net energy always stays the same!). Not only is it calculated that a closed universe probably has zero total energy, but a flat universe has a zero total energy as well. Negative energy has even been experimentally verified between two casimir plates.
(iv): If God exists, then conservation laws are contingent upon his will. There is nothing about them that are intrinsic to God, so there cannot be anything intrinsically contradictory about God based on an contingent law that he did not even have to create. If my opponent defends ex nihilo nihil fit, then he will have to explain why we should hold it as necessary. Many philosophers don't agree with it, like Wes Morriston and Quentin Smith. The idea that God is equivalent to "nonexistent" has not been justified either.
In order for Contention 1 from my opponent to stand, he must knock down all four of my objections. As it stands now, Contention 1 has been refuted sufficiently.
Contention 2: Omnipotence
My opponent is using a definition of omnipotence that nobody uses anymore:
"This notion of an all-powerful being is often claimed to be incoherent because a being who has the power to do anything would, for instance, have the power to draw a round square. However, it is absurd to suppose that any being, no matter how powerful, could draw a round square." - Internet Encyclopedia of Philosophy
All these incoherencies my opponent mentions are not a problem because Logical Omnipotence is how most philosophers view omnipotence. This started with Thomas Aquinas. The idea of God thinking of something he cannot do is not incoherent at all. If God exists, he could think creating a perfectly spherical cube. Since a perfectly spherical cube illogical, and something he cannot do, then he couldn't do it. This is fine, as logical omnipotence is only defined as:
"'Y is omnipotent' means 'Y can do X' is true if and only if X is a logically consistent description of a state of affairs."
As Matt Slick points out:
"God cannot do something that is a violation of his own existence and nature. Therefore, He cannot make a rock so big he can't pick it up, or make something bigger than himself." - Matt Slick 
Therefore, the reason this contention fails is because it is based on a definition that nobody uses anymore. Theists commonly hold the omnipotence of God to entail that he can do anything logically possible. These scenarios Pro mentions are, well, logically impossible.
This omnipotence paradox contention is easy to refute.
Contention 3: Omniscience
Can God know that he knows everything? Pro claims this is circular reasoning but this remains as a bare-assertion. If God knows everything, then the fact that he knows everything is just one of those things. There doesn't seem to be anything circular about this at all. Until Pro shows that this is circular reasoning, I see no reason to accept it off of an unjustified claim.
Now, my opponent states:
"Additionally, the being might think they know everything, and could be wrong." - Pro
If there is omniscient being, he would have to know everything by definition. Thus, if he thinks he knows everything, he has to be right necessarily. This argument from my opponent is a logical absurdity.
"What is knowledge? Is it a simple fact? If so, then even if you list off everything that God knows in an infinitely long list, you could still create a second list which just adds "God knows this:" in front of everything on the first list, creating a new list of things God doesn't know just as long as the first." - Pro
You cannot create a list of things God doesn't know, because if God exists, he knows everything as he is omniscient. This argument from Pro is simply incoherent by default. Any list you can make pertaining to God's knowledge, God would know about them all; no matter how many lists were made. This just means that your first list really wasn't everything that God knows, it was just the label you gave the list (you cannot have infinity +1 anyway, you can only add to a finite number). If the first list really was everything God knows, then it would include everything you could ever potentially say on a second list making a second list logically impossible; you couldn't do it. Also, if there was an infinite amount of facts, you would never be done writing the first list. Thus, the time would never come when you write a second list because you would still be writing the first. Even if you have another person writing a list, God would know both before either of you could ever finish. It wouldn't matter how many lists there are.
This contention falls flat on its face.
Contention 4: Omniscience/ Omnipotence
Pro argues that if God knows he is going to do X, then he has to do X, because if he doesn't do X, then that means his prior knowledge of doing X was false. However, if God has to do X, then he is causally determined by his prior knowledge and doesn't have have free-will; and is not omnipotent. The problem is that the fact that he is going to do X, is what causes his knowledge of X; it his not his knowledge of him going to do X which causes him to do X. Thus, God is still free as he is not causally determined by his knowledge and omnipotent in this scenario. Also, as I said earlier with regards to the definition of omnipotence, God can only do the logically possible. Not doing X even know he knows he is going to is logically impossible because it contradicts his omniscient nature. Therefore, even if God couldn't do it, he would still be omnipotent under the definition of omnipotence being that of the definition of Logical Omnipotence.
Yet again, another contention bites the dust.
My opponent presented four contentions in an attempt to show that God is impossible; all four are fatally flawed. I am an Atheist as well as my opponent, but these arguments are outdated and no good.
The resolution has not been established.
 Aquinas, Thomas Summa Theologica Book 1 Question 25 article 3