St. Thomas shows that the oneness of God is not exclusive in itself. For, this oneness is not the oneness of, say, a pan, The oneness of God is not the oneness of anything particular. I have cited one of Joshu's Koans to suggest that here is an common insight shared by Christianity and Buddhism as regards the notion or the oneness. I believe that the more we become aware of the problems of the contemporary world, like the conflicts caused by differences in religions, the more contemporary classical religious writings become. Some of the central insights of St. Thomas and Joshu have long been ignored.
Nothing is entirely new.
There is nothing entirely out of date, either. To devote oneself to the study of the past can be a most contemporary task. I believe that the study of the concept of oneness is one important way in which we can perhaps foster tolerance among the world's many religions.