God already knows who He can count on. Those souls were predestined before the foundation of this flesh age. Yet, God gives all His souls the opportunity to take this flesh journey without the memory of the age of the first rebellion. Flesh really does dull the senses of so many. But only the Creator can judge with perfection the heart/mind of each of His souls.
I do not consider myself called or capable of explaining to unbelievers what it means to have faith in something I cannot produce a graphic or photo. What does gravity look like? What does oxygen look like? Is it but a 'theory' they exist?
All souls/spirit intellect return to the Maker that sent them. The flesh body and intellect returns to the dirt from which it came. Some flesh intellect cannot/will not have the eyes to see or the ears to hear until their soul/spirit intellect returns to the Maker that sent them. Judgment of each and every individual soul/spirit intellect does not come until after every individual soul/spirit intellect gets a perfect education. Nobody goes to hell unwillingly.
No, their existence is not in dispute. There are theories to explain their nature and mechanics. Faith is not part of the discussion about gravity or oxygen. They are certainties.