You do not have to believe a word I say, it matters not to their truth. One mistake of unbelievers is that God requires faith for His truth to be true. One mistake of believers is that believing in something makes it true. Unbelievers, believers: faith does not work in the way you may conceive in matters of the spirit. If the unseen world does not objectively exist apart from all who believe it does, then it does not objectively exist. How can we know that it does exist, then? Does it have a consistent effect on the physical world? OK, this is for you to do if you don’t think it exists: pray, “God, if you’re there, let me know.” See if that does anything. See for yourself if the unseen truly does exist.
And for those who hold that one must believe in Jesus Christ, our Lord, to be saved, and that those innocent will perish in any case that they do not do so, remember the lesson of Saul turned Paul. This was a case of instant conversion, performed upon an unbeliever: so we know that God, by divine fiat, can save someone. Therefore it does not need, in that horrible question of faith, that they have to have heard and believed in the Good News before they die. Would not God save people in this other way if He could? For not a sparrow falls without His notice, and we are worth many sparrows. But it is the case that conversion does immensely help (first hand experience here).
Do you wonder about faith? You should, and what it means to you. How can you wish all the wrongs done you to be redressed, while all the wrongs you do to be overlooked? Yet this is the way people think; I know I have thought in this exact way. What will you believe when you face your Maker on the day of judgement? For we will be naked, of body, mind, soul, and spirit on that Day. Without excuse, will we all be. Do you wish to prepare for such an event? This is wisdom: forgive, as you want to be forgiven. Learn how to let it go, all the petty things. If they come back, let it go again. Until you are free.
Indeed, let me not be doubting, but believe. If nothing else, let me believe in the overarching idea: there is an unseen world, which is eternal, while the visible world is temporary. Why this is as so seems uncommonly wise, in my own eyes (though unworthy, they have seen many things). The reality of the spiritual world is different in nature than the reality of the physical world. It is true that many people have had many, often conflicting visions of what exists beyond our mortal pale, but one may conceive that — of those which are not purely imagination — they all may be joined in a logic of higher reason. Though I also hold it true that not all of what has been seen have any reality to them. Wisdom may be found in a science of such stuff. Science can be performed on anything, after all, and science is rather good at finding the fact of the matter.