I am not out to reinvent the wheel on this page. Instead, I’ll give you a brief answer to these questions then point you to resources for further study.
This is a question which contains many smaller questions such as, Does God Exist? Is there one god or many? Is God personal or transcendent? Can we know God? Did God create the world? Is God all-powerful/-good/-knowing? And so on.
Simplifying this, I can state, without controversy, that there is either some god or gods or there is not. I assert that there is. One way that this can be shown is by looking at the universe.
All things in the universe are contingent, meaning that they are dependent on something else for its initial and continued existence. The universe itself had a beginning about 14-15 billion years ago. Scientists today, generally, agree with ancient Christians and not ancient scientists that the universe has a beginning; it is not eternal.
As such, anything which has a beginning is contingent, not necessary. A contingent being cannot exist without a necessary being, for this would be absurd. That necessary being (although the term being is improper at this point) is what we call God.
This argument, and other’s similar to it, were developed largely by St. Thomas Aquinas, in his Summa Theologica. Peter Kreeft, a philosophy professor at Boston College, builds his explanations around Aquinas.
Next, a necessary being would necessarily be infinite, and there can only be a single infinite being. Thus God is singular; there is only one God. (Polytheistic systems generally do not hold any of the gods to this lofty philosophical status. They are greater and more powerful beings who are often at war–think of Q off of Star Trek. Plato debunked this idea fairly well in his dialogue, Euthyphro.)
If a being is infinite, it must be all-powerful/-good/-knowing (among other traits), otherwise it would not be infinite. This being would seem to be transcendent, but it most also have the capability of being personal if it is all-powerful/-good/-knowing.
Like an author creates his story and can freely remain aloof or enter into the story, so God creates the universe and can freely remain aloof or enter into it. Human experience provides good reason for believing that God would and did enter into the story. This is referred to as divine revelation.
Good resources for further study include:
- New Advent (Catholic news aggregator, Summa Theologica, Catholic Encyclopedia, Church Fathers)
- Catholic Answers (Publisher, Magazine, Radio Program, Discussion Forums)
- Peter Kreeft (Writings and lectures are free online. He has authored dozens of easily accessible books.)
Out of the major world religions, those originating in the near-east tend to have a vision of God that is active in human affairs. He revealed himself to people at some point in time either directly or through prophets. He continues to interact with the world through miracles and prayers.
Religions that have their origin in the east tend to have a god that is more aloof. Sometimes god or the gods interact with humans (as in some forms of Hinduism), and other times they are irrelevant, if they exist at all (as in most forms of Buddhism and Confucianism).
Once it is accepted that some god exists in some form, the next question is: what role does this god play in my life, if any?
There are many different answers that can be given, but the one that resonates the most with me is miracles. A miracle will never come from an aloof deity. Once that deity works a miracle, it is no longer aloof.
Seemingly genuine miracles (opposed to the common hoax) can be found throughout the religions of the world and their various offshoots and varieties. Any give miracle provides no proof or evidence for any particular religion. Even according to the Bible (cf. Rev. 13) miracles can be performed by Satan, if God allows it. Nevertheless, miracles are evidence of a god that is involved in the world.
Judaism and Christianity take the testimony of miracles and combine it with the authority of the written word and oral tradition (the Bible). Thus we have the Word of God, from the sacred Torah and the writings of the prophets, as well as the entire New Testament, which is all a miracle in and of itself, which contains prophesies and their fulfillment, which was more often recognized after the fact.
To these two pillars Judaism and Christianity add a third: God-given human reason. Although some Jews and Christians may forsake the value of reason, that is an error. God gave us our minds and our brains; he does not intend us to fore-go their use.
The strength in Judaism and Christianity relies upon these three pillars: miracles, authority of the writings which confirm themselves, and human reason.
I have spoken of Christianity and Judaism together, because Christianity is an extension of Judaism. But just as the Samaritans rejected YHWH by rejecting the prophets, the Jews do the same by rejecting Christ. Judaism is no longer the true religion of God, for they have rejected God’s Son and rejected their own writings in the process.
Some might wonder why I do not consider Islam or Mormonism with regard to Christianity the same way I regard Christianity to Judaism. The simple answer is that the Old and New Testaments are seamless in a way the Bible and the Qu’ran or Book of Mormon are not.
There are no prophesies of Muhammad or Joseph Smith, and no indication that the lost tribes of Israel made their way to the Americas. Nor do either of those texts contain and fulfill the message of the Bible in the way, as Augustine said, “The New Testament lies hidden in the Old and the Old Testament is unveiled in the New.” The Qu’ran is a syncretic text which combines Jewish and Christian writings with those of Arabia. The Book of Mormon is a product of one man’s imagination which took discredited 19th century theories of the origin of Native American and combined them with bible verses plagiarized from the King James Bible. Neither can be said to have the same relationship to the Bible as the New Testament has to the Old.
This will come soon. Check out resources above.