|Gottfried Wilhelm Leibniz, German philosopher and mathematician|
Premise 1--Every existing thing has an explanation of its existence, either in the necessity of its own nature or in an external cause.
Premise 2--If the universe has an explanation of its existence, that explanation is God.
Premise 3--The universe is an existing thing.
Therefore-- the explanation of the universe is God.
Since the universe is made of physical material it is a contingent object because no object can come from nothing. All contingent beings and objects must have a cause for its existence. The computer you are reading this post on is a contingent object that owes its existence to the people who manufactured it. Since the universe is a contingent existing object it needs a necessary agent to cause it, and the best way to explanation of the cause is an agent that is immaterial and eternal—that agent is God. In the computer example a contingent object’s existence is explained by contingent beings i.e. people, but the question remains what caused the people to come into existence. Prior to the big bang space, time, matter and the physical constants (such as gravity) did not exist. This means that physical contingent objects such as the universe need an explanation for their existence. God sparked the big bang 13.7 billion years ago and set the physical constants so that the universe and life could form.
The primary objection is that premise two is begging the question or making “the leap of faith” as some atheists like to put it. Since this premise posits the existence of God opponents will argue that is circular reasoning because the truth of the conclusion (that God exists) is assumed by the premises. William Lane Craig has this to say about this objection:
A. If atheism is true, the universe has no explanation of its existence.Another objection opponents like to bring up is the question what caused God? Notice that premise one deals with this objection by saying existing things can be explained by the necessity of its own nature. God is defined as an immaterial, eternal being and so is a necessary being. We can take God’s eternal existence as a brute fact. God did not come into existence or need a cause for His existence because He has always existed.
Since, on atheism, the universe is the ultimate reality, it just exists as a brute fact. But that is logically equivalent to saying this:
B. If the universe has an explanation of its existence, then atheism is not true.
As I pointed out in part I of this series opponents try to argue that the universe is a necessary object that has existed eternally, but as I said all attempts to show that universe is eternal have fallen short. It is possible that one day scientists will demonstrate how the universe is eternal or how the big bang started of its own accord, but right now God is the best explanation for why the universe exists. Even if scientists discover a natural explanation for the origin of the universe it doesn’t mean that God couldn’t have used those means to spark the big bang.