Why doesn't God intervene anymore? I'm admittedly not a believer, and one of the reasons is that God doesn't make his presence known. If he is out there, he seems to have come to the conclusion that humanity should be left alone.
There is a comprehensive answer to that question having to do with the role of the Holy Spirit throughout history and the difference between the era we are living in today and the 'pre-Christian' and 'Jesus on Earth' eras that are now behind us. But going into those details probably wouldn't be satisfying to you anyway. In a nutshell, God did not conclude that humanity should be left alone, God empowered humanity to guide the world towards the next era, thus why he works primarily through his people in the era we are currently living in.
I'm not saying miracles never happen anymore. I have been the recipient of a miracle myself and know of several others second hand. But rather that God's primary interaction with the world today is through his people, his image bearers whom he sent out into the word to be his hands and feet. It's different from how he interacted with the world prior to the arrival of Christ and the subsequent arrival of the Holy Spirit, but in many ways, it's better.
The more interesting question you pose is the following:
Amadeus said:
Aside from the Bible (or whatever religious text you subscribe to), what sustains your faith in God?
The short answer to this question is that I believe human beings are born with certain innate dispositions. Among these are some fairly strong desires for conditions that do not actually exist on Earth. We are born with a sense of fairness and justice, good and evil, right and wrong. We are born with a yearning for something greater than what actually exists on Earth.
There's three basic ways we can deal with that fact.
The first way is to deny that it is a fact at all and cling to the tabula rasa theory of human knowledge. The problem with this is that the blank slate theory has been very thoroughly disproven by now through sociological study. We pretty much know that innate dispositions are real and repeated attempts to prove that people are born blank slates have always failed. So this isn't a viable explanation anymore.
Another way to deal with this is to say that these must be biological imperatives that are the result of natural selection. In other words, we can conclude that having these desires has helped us survive as a species so natural selection has ensured people born without such desires were weeded out. This is a fairly strong and legitimate argument. I don't subscribe to it for reasons beyond the scope of this discussion. But suffice it to say that I don't find it as convincing as the third way of dealing with this.
The third way of dealing with this fact is to conclude that there must be certain objective truths that people are born with some awareness of (good, justice, fairness, etc.). If we accept this view we can proceed in any number of directions in exploring whence these objective truths come from, but the most straight forward answer is "God" (or, more specifically, "the divine").
At an intellectual level, I believe what I do because the story the bible tells fits observed reality better than the other alternatives. I believe it makes sense of all the desires we are born with (desires for good and justice and fairness) and fits the picture of the world around us the best.
Having said that, I think that is merely the intellectual underpinning of my faith. Ultimately, faith comes with emotional and not just intellectual aspects as well. I also believe in God because I believe I have felt his presence, heard his voice, and seen his life transforming power at work. Could this all be nothing but emotionalism? Sure. It's also difficult to explain to anyone who hasn't experienced it, which is why I leave it for here, as a side note in the end. But it's actually quite an important aspect of faith. It's just one that is difficult to discuss with anyone who hasn't experienced it.
I wouldn't say I never doubt. Everyone experiences doubt. Even Mother Teresa, long considered a paragon of faith in action expressed doubt in some of her letters. But doubt is good, wrestling with questions is good, religion is a contact sport. Besides, even if I were wrong about there being a God, living a Christian lifestyle would still be the best way to live.
If these kinds of questions interest you, I would highly recommend the following books:
A Search for What Makes Sense, by Brian McLaren
Simply Christian: Why Christianity Makes Sense, by N.T. Wright
