How the Shift Occurs

A theist (or theism in general) will normally make a claim (usually extraordinary in nature and without any substantial justification provided on their part) and then expect the atheist to disprove the claim they have just made.

Theist: "God is the creator of the universe and everything in it."

Atheist: "I disagree with that claim and am not convinced of God's existence based merely on your word that this is the case. Can you prove that your god exists?"

Theist: "obviously God exists. You can't prove that he doesn't exist!"

The fallacy committed is that the person making a claim bears the burden of proving said claim.

The theist, in this example, claims that their god exists, while the atheist is not making any claim. The atheist merely rejects the theist's claim due to insufficient evidence.

It is the theist's responsibility (burden of proof) to provide evidence for his claim.

Extraordinary claims require extraordinary evidence!

Atheists are generally agnostic (as they do not believe in and are not convinced of any particular gods' existence, but are not so arrogant to assert knowledge that gods do not, in fact, exist).

Theists are generally gnostic (as they do believe in and are convinced of their particular god's existence, as well as are so arrogant to assert knowledge that same does, in fact, exist).

Atheists who claim knowledge of the non-existence of a god or gods bear the burden of proof in that instance.

However, I believe that due to the fact that theists have failed to submit sufficient evidence to satisfy their claim of the positive assertion (God does exist) - having been given sufficient opportunity to do so - that it is reasonable to conclude in favour of the atheist’s negative claim that God does, indeed, not exist.

That being said, one should never be expected to prove a negative assertion, since this (disbelief) is the default position on any subject.

Lollipop the Unicorn

To explain the above by way of example:

I claim to know an invisible flying talking unicorn who farts pixie-dust and sings me to sleep every night. This is how I'm able to get such fantastic sleep - because of his singing - and, in exchange, I have to do whatever he says.

His name is Lollipop and he is the reason why we all sleep. Without him, we'd never be able to sleep and would die of exhaustion.

I further claim that only those who truly, genuinely believe in his existence can see him. If you can't see Lollipop, that just means you aren't a true believer. Moreover, you have until death to believe in him otherwise you'll suffer a restless and sleepless eternity (always tired but never able to sleep).

If you cannot see him, that's not necessarily a dealbreaker, because he has also given me a list of instructions which, in addition to believing in him on faith alone, you have to follow unquestioningly for the remainder of your life... otherwise you'll suffer a restless and sleepless eternity.

You need to be willing to give up your life for him. Everything you do from now on is in service to him. You will worship him and he will continue to bless you with restful sleep.

Now I say to you, dear non-believer (threats of eternal restlessness notwithstanding), how dare you disrespect Lollipop like that by not believing in him? After all the sleep he has given you. If it wasn't for him, you'd never be able to get to sleep. How do you explain sleep if not for Lollipop? can you prove that he doesn't exist?

If you didn't think I was absolutely insane at this point, you'd have bigger problems than Lollipop the Unicorn.

Just like it is not up to you to prove that the Loch Ness Monster, Bigfoot, Pixies, Leprechauns, the Flying Spaghetti Monster, Lollipop the Unicorn and many other supernatural entities do not exist, it is not the responsibility of disbelievers to disprove the existence of your particular skydaddy.

Just don't expect us to take it on faith or take your word for his existence under threats of hell or promises of heaven. We want actual facts, hard evidence and rational, reasonable and logical arguments for his existence, grounded in reality. We want proof BEYOND A SHADOW OF A DOUBT.

Standards of Proof in Law

A balance of probabilities - this standard of proof requires that something is more likely to have occurred than not - i.e., the probability that an event took place is greater than 50%

Beyond a reasonable doubt - this standard of proof requires that one be convinced of something completely; that all reasonable doubt in their mind be removed. Proof beyond a reasonable doubt means that enough evidence has been presented (and insufficient contradictory evidence has been forthcoming) to remove so much doubt as regards the truth of a particular claim that, to deny it, would be irrational.

How this applies to religion

"He who alleges must prove" - one of the most basic principles in law.

This, however, is a principle that also has its roots in logic - that is, reasoning conducted/assessed according to strict principles of validity.

If somebody makes a positive assertion of fact, it follows that they must first supply sufficient evidence to support that assertion and, only when their position has been reasonably validated and proved, shall the onus shift to the party wishing to disprove facts which have now been proven.

Only once the party making the positive claim has sufficiently discharged their onus, does the burden shift to the opposing side to disprove what is now taken to be true.

When it comes to religion and matters concerning the existence of God, people are claiming things to be true (positive assertions) and, therefore, bear the burden of proving such claims.

And, although science, biology and logic cannot be expected to disprove something that hasn't been shown to exist - lack of evidence of anything is, in and of itself, sufficient evidence of its non-existence; that is, until sufficient evidence is presented to confirm that something does, indeed, exist, we are entitled to take the default position that it does not - they have, nevertheless, presented evidence (in the pursuit of discovery, not in an attempt to disprove scripture or god, just to be clear) that overwhelmingly invalidates many of the claims made by theists and their scripture.

Consider the following hypothetical example as it relates to theism:

X is accused of murdering Y (X murdering Y being equivalent to god existing, creating the universe or being responsible for the events that have taken place on earth) and the prosecution (theologians) must make their case to support this premise (as is their burden to bear).

the following is the evidence they present to the court:

1. unverifiable eyewitness accounts, by people they cannot find, nor show to even exist;
2. The prosecution is able to submit the (poorly) written testimony of non-eyewitnesses who, although can be shown to exist, also cannot be found to give oral testimony and be cross-examined;
3. Those that can orally testify are only able to do so based on their understanding of the written testimony provided by the aforementioned non-eyewitnesses;
4. contradictory reports and information about the circumstances surrounding the crime;
5. experts for the prosecution can only go as far as confirming certain dates, times, people and places but not anything really relevant to the crime itself;
6. most of the expert testimony submitted actually discredits the prosecution's case, short of outright destroying it.
7. the prosecution cannot submit documents of X's identity, let alone bring him to trial, yet claim they definitely have a case against him for murdering Y and assures the court that he absolutely does exist (maybe if they just had a little faith 😜);
8. not to mention, it appears as though a crime wasn't even committed in the first place (i.e., on the face of the facts before the court, it doesn't seem as though Y was even murdered, but rather that he committed suicide).
9. No competent prosecutor would ever dare bring this case before the court and no competent court would ever entertain such a case.
10. It is thrown out immediately.

Note that atheists are not saying, nor should they be expected to conduct such investigation on behalf of the theist to disprove this, that the god of theism did not create the universe, everything in it and oversees anything that has happened, is happening or ever will happen.

However, none of this negates the infinite number of possibilities that may exist, of which your god being the proximate cause of our reality is just one possible explanation.