Do you wish there's a god?

[Belacqua]

So how do you go about deciding what is real or not meant to be taken as real ?

And how do you think theologians go about deciding the same question ?

How do we go about studying any complicated subject? 

Sincere and open-minded study. Patience. Humility. Lots of discussion and even more reading.

Here is another way in which emotion may determine outcome. In cases of subjects which aren't immediately practical, people usually have to love the subject before they study it. As with music, someone who already loves music is way more likely to study its practice, theory, and history. Nobody studies music for twenty years and then makes up his mind whether he likes it or not. 

This is NOT to say that we should study anything with preconceptions and work to shore them up. It's just to say that beginning with a dislike of something is unlikely to lead to any sincere effort.