I've just left this comment on a previous post, arising out of an interesting discussion with someone who left a comment (and I'm always very grateful for comments): The doctrine of the Trinity is one of those things where I believe because the Church has told me. It seems to me that the Arians had a spectacular proof-text in John 14:28 "The Father is greater than I". The fact that the Arians were rejected as heretics convinces me that proof-texts aren't the way of interpreting the Bible. My own belief in the Church is prior to my belief in the Bible and based on other evidences. I'm aware that all sounds very pompous and nasal, put like that; I was just trying to be concise.
St. Augustine famously said: "I would not believe the Gospel if the authority of the Catholic Church did not move me." I'm quite willing to admit that I come to faith in Christ through my trust in the Catholic Church. This trust is based on viewing the history and life of the Church as a whole, over centuries and continents-- volumes could be written finding fault with this or that aspect of its history or influence or practice, but this fact doesn't dent my faith. The Church really does behave, as Chesterton said in The Everlasting Man, like the bearer of a message, and not its inventor.
This doesn't mean that I think everything a Pope says is right, or everything a saint says is right, or even that the Church has always been wise or enlightened in all its actions. Pope Leo X condemned Martin Luther for opposing the burning of heretics! Saint Ambrose of Milan refused the Eucharist to an Emperor who had demanded the rebuilding of a synagogue burned down by a Christian mob. It's quite easy to find such scandals, reaching into our own time.
But if you take an overview, the consistency, sublimity, wisdom, and goodness of the Catholic Church-- compared to all other institutions-- is startling, and to me bespeaks a supernatural origin.