The question of belief in its colloquial sense (without proof) implies that the beholder of the belief lacks knowledge in order to make a decision out of certitude.
As an example,
*”He has faith that the hypothesis would be substantiated by the fact”. - Dictionary.com
Until proven otherwise this assertion is faith-based.
Atheist’s know insufficient to claim certitude of no god/s
It is therefore my assertion that atheists despite the definition of the word itself a-theist, a person who denies the existence of god/s, in the practical sense, must make this assertion based on knowledge. Considering no one has all knowledge or is not omniscient and there is the potential for extra-dimensional or metaphysical knowledge (even if only hypothetically) an atheist must invoke an act of faith. A hypothesis that needs to be substantiated by the facts. They do not know enough to say with certitude that a god, some where, any god, does not exist. Not with absolute certitude. Not when earth is potentially but a speck in a multitude of “multiverses”.
Theists know insufficient to claim certitude of god/s
This can be true also for theists. Any theist who accepts belief in at least a god on the basis of intellectual assent, must invoke belief to bridge the gap of knowledge to say with certitude a god exists for the same reasons atheists do. It’s a hypothesis that needs to be substantiated by the facts.
Theists need just one fact encounter to dispel faith
But while atheists must possess omniscience in order to invoke a certitude of knowledge concerning atheism, and avoid a faith based assertion, theists on the other hand don’t need to possess omniscience, they need to only encounter one god, one time. Upon their encounter, their faith based acceptance changes to a certitude of knowledge that at least one god exists.
The non material
We generally are taught a reductionist understanding to our existence. Yet there are certain things that are immaterial. Take for instance the mind. The mind is coupled into a brain, which in turn is housed in a biological machine. The machine limits the brain’s functionality and the brain in turn limits the mind’s functionality. But the mind itself is immaterial and exists outside of the body.
The healthier a person, the greater chances that their brain will have an optimal state of functionality. Granted what hardware was created due to the genetics is a limiting factor on the brain. The brain limits the mind. Information is fed into the mind via the body and it’s senses. A lobotomized person that has had hardware removed limits the mind to acrue new data or possibly even retrieve old data. A person who has had the part of the brain for feeling pain removed, cannot input pain into the mind, certainly no physical pain information can be registered.
The brain comes with preprogrammed functions that work on the body and does not require the mind’s input. This distinguished the brain from the mind. The input of language, software and data uploaded via the brain into the mind limits the mind. A blind person from birth cannot input visual data into the mind. The mind, brain and body are intricately linked.
Experiencing the immaterial
When someone experiences their own mind, they don’t doubt that they have a mind. They interact with their mind even though it is immaterial.
In the same way when people have experienced a god and interacted with him they don’t doubt that just because it was immaterial that the god was not real. Being of another dimension or not of the physical dimension does not discount its existence.
It is true that some experiences can be fabricated by our own minds but not all. Just because we experience something in our own mind doesn’t immediately rule out interaction with another mind.
It is true that the brain processes the information and that the body facilitated and reacted to the experience physiologically and physically. But the experience though felt it source is non physical.
Concluding remarks
It takes just one experience of a non material deity to switch from faith-based theism to theism with certitude.
This certitude is compounded if and when the deity interacts with the physical world.
I’m not arguing for a particular deity, I’m merely asserting that interaction with just one deity, true deity or self-professing deity is sufficient to change the status of a theist or atheist for that matter. Sure, it’s normal to try and explain it away, but if you’ve interacted with an intelligence/mind that is not your own intelligence/mind which gave you knowledge or experiences that could not have originated with you, whether true or false, verifiable or not, you cannot attribute to your brain something that was created by another mind.
Therefore theism is both faith-based for those who are still hypothesizing and factual for others who have substantiated their hypothesis with facts.