What exactly is “purpose?” I would say it has to involve happiness as experienced by some object or being. Also, for an object to have a genuine purpose, that purpose must be eternal in duration; otherwise, it may as well not have ever had any purpose at all.
A: What?! Why?!
B: Because of the (pre-assumed) endless continuation of time. Even if a purpose lasts for exactly a thousand years, it’s as good as zero when comparing it to the millions and billions of years that follow in eternity. I’ll talk a bit more about this at a later time.
As far as we know from what science tells us, everything eventually ceases to exist, including so-called “non-living” things, at least in their current state. I believe the 2nd Law of Thermodynamics implies that everything in the Universe will eventually break down into energy, and this event is referred to as the “Heat Death of the Universe.”
A (suddenly worried sick, looking pale, and about to burst into tears): THE HEAT DEATH OF THE UNIVERSE?!
B: Calm down! Don’t worry, it’s predicted to not come about for another, oh, approximately one bajillion years.
Here, why don’t you drink some more lemonade.
Anyway. What was I saying? Ah, yes. I was going off about “purpose.” So what interminable purpose could our existences possibly serve?
Definition. A state of existence of something has a purpose if that thing, while in that state, has potential to make a permanent/eternal difference in the total amount of happiness experienced by one or more other objects in the Universe, regardless of the size of that difference.
Therefore, if nothing in the universe is different (or ”better,” or has been helped, or improved) after something has passed through a certain state of existence, then that thing may as well have not existed in that state at all. By this definition, if there is no God, and no afterlife, then nothing has a purpose, since everything is mortal, or will not last eternally in its present state of existence, and eventually in no state of existence at all. On the other hand, if there is a God, then by this definition EVERYTHING has a purpose, assuming God created all things. If He did, then it was for whatever (eternal) purpose He wanted those things to fulfill. For instance, certainly each of us has a purpose in this (mortal) state of existence, if it affects what becomes of us in our next state of existence, whatever that is.
A: Are you saying that God defies the 2nd Law of Thermodynamics?
B: If God is to be eternal, then I suppose He does! Is therefore the 2nd Law of Thermodynamics a proof against the existence of an eternal God? No, since, as we’ll see later, scientists cannot guarantee eternal truth, due to the assumptions they make – for example about the constancy of nature and its laws – that they don’t know for certain that they can make. No scientists can guarantee that any “law” they may come up with is eternal.