Here are some things to think about.
1.) This is not a Christian problem. Christians and non-Christians must account for the same dilemma:
First of all, if we are going to talk about WHY is there something rather than nothing, and WHY is there anything here at all... that is not merely a problem for the theist. Both atheists and theist have to answer this same question. Christians and non-christians both face the same philosophical dilemma... so it all comes down to a matter of who has a better explanation.
2.) The dilemma and past cosmology.
In times past, people thought the universe was eternal. They believed "stuff", or "matter", had just always existed, and always been here. At no time did the atheist ever posit an explanation for WHY the matter was here to begin with... they just said "it's always been", and that was that. No further explanation given or required.
Now, it was reasonable to assume that SOMETHING had always existed, because of the philosophical proposition EX NIHILO NIHIL FIT.
This means "out of nothing, nothing comes."
This is the Latin philosophical expression for a thesis first attributed to Parmenides, in one of Plato's works, in the 5th century BC.
This understand that "nothing comes from nothing", is philosophically sound, scientifically sound, and also aligns with our common experience in life.
As some theologians have put it:
"If there was ever a time when there was nothing, there would be nothing still."
To clarify: theologians never thought the "universe" was eternal, but they did think that "something" was eternal, and that something was God. They didn't just believe God WAS eternal, but that he MUST BE eternal... because something had to exist eternally, or there would be no explanation for how anything ever came to be. "Out of nothing, nothing comes."
Something cannot come from nothing.
So if there is something here now, then something, something of some kind, had to be eternal... or nothing could be here now.
So in past cosmology, everyone believed in the eternal.
Atheists believed the universe was eternal.
Theists believed God was eternal, and he created the universe.
Since there is "stuff" here now, and it cannot come from nothing... then SOMETHING had to be eternal.
3.) The dilemma and modern cosmology.
So atheists thought the universe was eternal... and then one day that all changed.
Edwin Hubbel discovered the red shift, and in 1929 reported that the red shift was proof that the universe was NOT eternal. The universe had a beginning. Then other discoveries were made which corroborated this conclusion about the universe having a beginning. Now, it is widely accepted, and science does indeed seem to show, that the universe was not eternal, but had a beginning. This beginning is referred to as the Big Bang.
The universe (comprising ALL matter, space, and even time) was not eternal. And for some inextricable reason, at some point, it simply came into being.
The theist has no problem with this, because all of these discoveries fit perfectly with his beliefs.
But the atheist is in a terribly quandry... he's left trying to explain why "something" suddenly popped out of "nothing."
This has led to endless debates, and even terrible philosophy books written by famous physicists who don't know anything about philosophy. (Cough cough, Stephen Hawking.)
4.) The dilemma, as reconciled in Christianity.
A.) The atheist has no explanation for any of this, other than "something popped out of nothing"... which is impossible in both physics and philosophy. It simply cannot happen.
(Physicists will sometimes claim it is possible in physics, but then they go on to equivocate on terms, and essentially state a different case altogether. Essentially, they have no explanation, so they come up with a fake explanation they try to pass off by changing definitions of words. It's what very smart people often do when they can't win an argument... they begin to lie, and cheat by changing the argument to something else.)
B.) The Christian, however, has a very sound and coherent explanation.
There IS something eternal, which is God. And this eternal being created the universe, which we know is NOT eternal.
This is all logically coherent.
Keep in mind, that for centuries, if not millennia, atheists thought the universe was simply eternal... they NEVER HAD ANY ISSUE WITH SAYING SOMETHING WAS ETERNAL.
They didn't need to explain it, they didn't need to figure it out... they were fine just saying the universe was eternal.
They had no issue with the concept of something being eternal.
They only have an issue with the concept of "eternality" if the eternal thing is God... an eternal thing which they dislike.
CONCLUSION:
A.) There is nothing illogical about claiming something is eternal. Atheists, until recently, never had any philosophical problem believing in the eternal.
B.) Many atheists STILL believe in the eternal. Many believe certain abstract objects are eternal... things like math, moral virtues, or natural laws.
C.) So atheists have NEVER had a dilemma believing in the concept of the eternal, and many still do believe in the concept of the eternal (many physicists claim laws of physics, like gravity, are transcendent and eternal)... so atheists clearly have no problem believing in the concept of the eternal.
D.) Something MUST BE ETERNAL, or there would be nothing here now. From nothing, nothing comes. If atheists believe in the eternal, and require of themselves no explanation of how anything eternal came to be... then Christians certainly have no burden or liability to explain the eternal either.
E.) We have no explanation for how God came to be, except that he did not. He did not "come to be", he has just "always been." If it's any comfort, consider these 3 final points:
1 - atheists have no issue with the concept of eternality when it comes to the particular things they believe in.
2- something, something of some kind, MUST be eternal... as eternality is an absolute necessity of logic, philosophy, and physics... if SOMETHING was not eternal, then nothing would be here now.
3 - God truly is the best logical explanation for how all things came to be... but that is a different set of arguments.
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