I believe in the Biblical God as much as I believe in Zeus, Isis, Thor and a thousands of other (dead according to Nietzsche) gods. This might sound like an eyebrow raising statement, especially those who know me since high school, but six years of trying to reconcile different cultures and religions have prompted me with this statement.
I think it's safe to say that I was the prodigy of the religion department back in high school. I spend hours drinking coffee with my religion teacher trying to solve morality (and you can even say) philosophical cases. Can God be seen in abortion or prostitution? Will Christianity or Islam fade like the myths of the Greeks and Egyptians? We answered these questions very liberally relative to being in a Catholic school. It was a good exercise, but I did not realize that questions were starting to pile up unconsciously and force me to go beyond religion and culture, trying to asses what this whole faith means to us.
Richard Rorty said that truth only exists in so far as where there are sentences - meaning we create these truths, these mutually accepted delusions. Truth is not something out there that humanity has to find because more often than not (and you can base these from your own experiences) these truths are dehumanizing - hindi makatao. These delusions aren't bad at all because they help us cope with our day to day activities, which I think is more important. It can go as broad as religion's ability to organize people to as mundane as people calling that hot ball of gas SUN.
Having mentioned that, the reason I believe in all the practices of faith (together with their head deities) is that they prove useful to each individual or group in a particular period of time. I think exercises of religion is relative on each one of us since truth cannot be out there - we create the truths, these mutually accepted delusions. We are formed by different historicity and experiences therefore no one interpretation of the "pagpapakita ng meron" is enough.
My mom and I always have debates every Sunday because I don't want to go to church. She took up a lot of philosophy courses and is a very devout Catholic, so it's always a good debate but she tends to lose sometimes when I use the argument of multiculturalism. And it's quite ironic that the more she tries to convince me to go to church, the more that I realize the relativeness of this whole religion thing.
Amidst all of my pietious abstinence, I have to admit that I am left longing for the presence of God. And it's this personal experience of theological hunger that allows me to conclude that yes, there is a God, but he/she is beyond organized religion or any form of human practice. But we need religion, because we humans are weak. Religion is a celebration of life, of being in a community; therefore is a human necessity.
(Sorry for leaving the thought hanging but the totality of the topic cannot even be captured in a thick volumed book. I just had to write this down while waiting for my sundo in school to organize my thoughts.)