I'll say it again: faith makes me believe what I believe. Why do Muslims believe in Allah? Why did pagans worship animals and trees and celestial objects? One might say you can't know that God exists. But faith is a phenomenon that doesn't happen overnight. It's often ingrained in a person's being. What a person believes in usually takes years or decades of learning about religious doctrines and a lifetime of tradition and practices. The essence of faith becomes a part of a society's culture.
But enough about my faith. All I can say is, a lifetime of experiences and teachings has led me to believe what I believe in, and I derive spiritual fulfillment from that.
I'd like to hear about your beliefs.