The Kalam Cosmological Argument is an excellent logical argument for the existence of God. It was originally developed by Muslim philosophers (don’t freak out, they’re Theists too) and later added to by Protestant Apologist William Lane Craig. It only proves Theism (God, of a sort, exists), not Christianity specifically, but it is a very solid proof. Roughly, it looks like this:
- Everything that begins to exist has a cause.
- The physical world (including time itself) began to exist
- Therefore, the physical world had a cause. (Presumably God. More on that later.)
Now this argument is clearly logically valid (the conclusion flows from the premises), so the only way an atheist can refute it is by attacking the premises. The first premise is generally accepted. After all, it is true for every single case which has been tested. Everything that we know of that began to exist has a cause for coming into existence (not including the universe itself, since that is the thing to be proved). Chairs come into existence because of carpenters, storms come into existence because of weather fronts, etc. The first premise is just as certain as any scientific fact, or perhaps more so.
An atheist could really only refute the second premise one way: to say that the physical world (including time) has always existed. If time has always existed, it means that the past is infinite, but this cannot be true. To explain why, let’s look at Aristotle’s two definitions of something that is infinite:
Potential Infinite: A potential infinite is something that is
not, at the present moment, infinite. It is something that is
becoming infinite by a repeated process (such as adding one to a number). If the process were to continue indefinitely, in theory the thing would become infinite. This is what is used in mathematics. (such as a line or pair of coordinate axes extending indefinitely, or a number being divided an infinite number of times to create an infinite number of decimal places). If the atheist is merely saying that time is a potential infinite, then he would have to admit that the past is finite since everything that is a potential infinite must start as something finite.
Actual Infinite: An actual infinite is a thing that is infinite now. Described as “a complete set of an infinite number of things”. The past cannot be an actual infinite since an actual infinite cannot be “traversed”. If one sets out to cross an infinite distance, he will never arrive at the destination. We have come from the past to the present, which means that the past has been traversed, which means the past must be finite, which means that time must have had a beginning.
This means that the physical world must have had a first cause, but what does this argument prove
about the First Cause? It proves that He must be non-physical, outside of time, eternal, powerful, creative, and personal (i.e. He is a person, someone with a will, not a mechanical, cause-and-effect force). The First Cause must be personal because if He is the only eternal thing, then what could have caused Him to create the physical world other than Himself? It must have been done by His own choice and for no other reason, which means He has a will.
Here are some links to some of the research I did on this:
philosophyofreligion.info/theistic-proofs/the-cosmological-argument/the-kalam-cosmological-argument/
philosophyofreligion.info/theistic-proofs/the-cosmological-argument/the-kalam-cosmological-argument/maths-and-the-finitude-of-the-past/
sites.middlebury.edu/fyse1229pisapati/mathematical-work/potential-infinite-v-actual-infinite/
en.wikipedia.org/wiki/Actual_infinity