How are we supposed to pick the right one when there are so many?
Define "right one." It all depends on what you're looking for. Are you lacking structure, and seeking it? Are you looking for comfort or hope? For the fellowship and companionship of others? Truth? Are you trying to fill an emotional hole that you don't know how to explain? Or are you seeking answers to questions regarding what came before...and what will come after this life? Picking a religion (or choosing not to) is a very personal decision.
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How are supposed to know which one is the right one?
There isn't any way to "know" if what you're choosing to believe is true. Faiths are founded on belief...not on fact. Or if you're looking for a definition in biblical terms: "faith is the substance of things hoped for and the evidence of things not seen." However, if by "right one," you mean something other than truth...then it all depends on what you're seeking. Whichever one fulfills what you seek...that's the "right one" for you.
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Should we choose the religion that's most attractive to us?
If you really must choose one...then I'd say you'll have to do this if you want to be happy with it. Doing anything else is like choosing to wear a shirt that's 2 sizes too small and expecting to feel comfortable.
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Can all religions be right?
No. Many religions contain the concept of exclusivity. Essentially saying that they are the only correct faith, and that followers of all other faiths are heathen, immoral, etc. Example: Christianity vs. the Semitic (ie. Canaananite/Babylonian ) religions found in the old testament.
Athiest (which sometimes can be seen as a religion of science) vs. any religion. Etc...
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Are those of us who follow any religion fools?
Matter of opinion and perspective. Staunch athiests will say yes. Staunch followers of any religion will say no...unless of course you don't follow their religion...and then some of them will say you're a fool too.
Personally, as an agnostic, I've put a lot of thought into the complexities of perception/reality that define this existence. It's not a simple thing. Most people want to believe in the simple and concrete, while ignoring what they don't wish to see, or can't account for within their belief system. It's a complex world, one that often seems easier for those who are ignorant of its complexities. I don't begrudge anyone their right to believe whatever they want to...so long as they don't try to force those beliefs on others. Religion does give comfort to some, and helps others by giving them something to hold onto. (I'll skip the list of negatives for now) It isn't foolish to seek something that you're missing, or are in need of. However, some become so inured in the dogma that they lose themselves, and their ability to think outside of those constraints. To lose ones self in that way, is what I would consider foolish. Like any tool, religion isn't necessarily good or evil...how it is used determines whether or not the wielder is a fool.
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How do we balance the equasion of thought & beleif?
Again, a personal decision. As complex as balancing your thoughts and emotions. Everyone has a different balancing point. Some set their point while young, and never budge...often stunting their growth. Others grow over time, and find the need to rebalance their beliefs to fit new ideas from time to time. It's more a question of what you value, and in what way you value them, as to how you balance the two.