This is me pondering faith, and why we think the way (or, in the manner [process?]) we do (or, don’t).
Scientific validity is not the result of scientists abstaining from making value judgments; it is the result of scientists making their best effort to value principles of reasoning that reliably link their beliefs to reality, through valid chains of evidence and argument.
So, perhaps an answer to the (two-part) question – “What should I believe; and, why should I believe it?” is generally a scientific one:
Believe a proposition because it is well supported by theory and evidence.
Believe it because it has been experimentally verified.
Believe it because a generation of smart people have tried their best to falsify it – and, failed.
Believe it because it is true (or seems so).
This is a norm of cognition as well as the epistemic core of any scientific mission statement.
This may-or-may-not be related. But, if you want to go deep, consider the theory of “Probabistically”. /1
Or, perhaps you believe it (a thing, or any thing) because you simply trust your heart and instincts.
Or, someone you know, and like, inspires you to cast aside science, and make the leap.
There is also the option of believing in a thing only because you want it.
All this aside… I believe in me – and my discerning judgment.
Peace be to my Brothers and Sisters.
1/ I did not make this word up (this time). Consider… Nassim Nicholas Taleb