"Listening to Rubber Soul didn’t clarify my ideas for Pet Sounds, exactly. But it inspired me. When we were listening to it that night I said to myself, “Now I’m gonna make an album just as good as Rubber Soul.” Not the same album. Obviously there can only be one album that’s Rubber Soul, just like there can only be one Pet Sounds. But it inspired me to do my own thing, and so the next morning I went to the piano and wrote God Only Knows with Tony Asher."
http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/music/beatles/article6818698.ece