Wade G. writes in his Evolution of the Mystery blog a really nice summary of Tillich's conception of God as our Ultimate Concern. He closes with the following comment:
But, regarding Tillich's conception of God as I understand it... I find that when my days are going rough, it is soothing to the spirit somehow to take a deep breath and ruminate on all of this. I'm not really sure I can express what my "ultimate concern" or "ground of being" is. I just know, somehow, that it is there - that life is not surface only, but deep. It has nothing to do with anything "supernatural" or anything that contradicts the rules of physics or my own perceptions. The closest word I can think of to express my "ultimate concern", which seems to just about fit, is that very simple one "love." Not love of something particular, but love in it's limitless and mysterious ideal. And maybe that is not far off from what the author of the first letter of John was telling us when he said (in the New International version translation) "Whoever does not love does not know God, because God is love."This comes very close to my own understanding. Religion for me isn't about believing in miracles, or in the supernatural, or anything that contradicts the laws of nature. It is instead about a sense of awe in response to the depths of meaning, creativity, love, and purpose.