For me, it was reading through parts (no, I didn't read the whole 26 volumes) of St. Thomas Aquinas' Summa Theologica. Aquinas (a monk) wrote these things in the 1200's. He applied Aristotelean logic to the Catholic faith. It's the only time that I've EVER seen a faith try to prove itself logically. Some of the stuff is questionable. He does have some very solid arguments for his faith, however, such as his 3 proofs that God exists. Most religions to me seem to be basically faith alone. It's very comforting to me that my chosen religion has also employed sound logical reasoning in what it teaches.
Here's a link that goes into detail on it...
http://www.harvestfields.netfirms.com/etexts/52/06.htm
What led you all to choose your religion?
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