I guess it depends on the specifics of the subject of his happiness. He could speak to both religious systems, reminding many people of both of what they have forgotten.
Come and hear (phraseology from the Talmud) how the Jews split hairs in “don’t worry be happy.” Check out this story. (to long to cut/paste so link here:
http://www.chabad.org/library/article_cdo/aid/112045/jewish/Nahum-Ish-Gamzu-and-Rabbi-Akiba.htm