In appreciation for Michael's post below, I want to add a bit of biblical back-up for that great theologian Chico Marx!
This week we read at Morning Prayer John 9, the story of the man born blind. It is, in many ways, the classic text for an empirical theological mode. While fear of losing power (the Pharisees in the story), or fear of being thrown out of the synagogue (the blind man's parents) prevent those around him from seeing what is right before their eyes, the newly cured blind man expresses his incredulity at their (newly acquired) blindness: "The man answered, ‘Here is an astonishing thing! You do not know where he comes from, and yet he opened my eyes!'
This, it seems to me, is one place to start in distinguishing what I would call the tradition of 'religious left' theology, the kind of progressive theology that we see in Reinhold Niebuhr earlier in the 20th century, or in Rowan Williams' more recent work on a theology of sexuality. The abstract deployment of scriptural texts, or the convoluted turns of some natural theology arguments are simply no match for the eye-opening witness of healing, grace and love that so many have seen in same-sex couples in our parishes, and for the blessings of prudent, non-exploitative family planning.
Unless one employs a blindingly rationalistic theory of the 'noetic effects of sin' such that we can't trust our own eyes, the catholic faithful, as Michael's post gives evidence of, have seen far more of the truth of things than some in power (and in fear of losing that power) can imagine.
In listening to the remarkable words of Maureen Walsh, the conservative Republican from Walla Walla, as she speaks of her passionate love for her lesbian daughter, I for one hear the deepest meaning of what the First Amendment calls the free exercise of religion. Free from fear, free to rejoice in the blessings that come as gifts to us, right before our very eyes.