1. As with, say, colour perception, reports on the direct experience of feelings are necessarily veridical. E.g., you cannot report (in good faith) that you are experiencing fear, while not in fact being afraid.
2. This experience reveals that fear is real. One needn't go looking for fear in the world, as one would go looking for bigfoot or quarks. This is just not what we have in mind when we attribute reality to certain things.
3. I experience love.
4. God is, by definition, love.
5. Therefore, God is real.
Issue will be taken, of course, with step 4, as having a stipulative character. I am taking it from 1 John 4:8, but others will look to other biblical passages and to other religious traditions to say that God is an anthropomorphized being of some sort, or a theriomorphized one, or a many-headed chimera: in any case, a conscious agent, not a feeling.
But here one might also note that any virtue or feeling at all can be, and often is, anthropomorphized: justice, beauty, purity, etc., have all been represented as human beings in the history of art, and a future historian or a Martian anthropologist would be forgiven for inferring, for example, that late-modern New Yorker-New Jerseyans follow a cult around the goddess of liberty.
more here.