It was pointed out to me recently that Watts really wrote this song about the expectation of Jesus the Messiah's triumphant return at the end of history rather than about his entry into the world as a baby in Bethlehem. After all, there are no mentions of mangers. Or shepherds. Or wise men. Or Mary. Or reindeer. (Just checking whether you're paying attention, ha!)
He did base the song on the last half of Psalm 98:
Make a joyful noise unto the Lord, all the earth; make a loud noise, and rejoice, and sing praise. Let the floods clap their hands; let the hills be joyful together before the Lord; for he comes to judge the earth, with righteousness shall he judge the world, and the people with equity.But to me the wonderful thing about the song is that it is a near perfect expression of the mystery of the Kingdom of God. Throughout the Hebrew scriptures (AKA the Old Testament) the story of redemption was wrapped in a paradox. YHWH promised that he would rescue the whole earth from their sin and rebellion, and he would do so through his people Israel - not just for them but through them. And it also was filed with a promise that the God would one day exercise his right as King over everything. But...the promise contained interwoven passages of a triumphant reign and the fact that the Messiah would suffer to bring it about.
Israel's king but also king of the world (no Titanic jokes please)? Coming in power to rule but also coming in humility to suffer? Huh?
But both were (and are) true! God entered the world in a tiny town as a little baby. He lived, taught, and suffered in order to rescue his people from sin and begin the reign of God's kingdom. And he will come again to bring heaven and earth together, setting everything right once and for all.
So, as I read it, there is no reason to separate Christmas from his future Glorious Appearing. It's all part of one wonderful story that we are privileged to participate in. To insist on Watts' hymn being about one or the other is to make the same mistake the religious leaders of Jesus' time did; to do so is to miss the fact that the triumphal return in dependent on the mission of Jesus. It's one unified plan.
So joy to the world! The Messiah has come to initiate his kingdom, through his suffering and death. He reigns today through the subjects of his kingdom and he will come again to set everything right. Psalm 98 is not about just one part of that, and neither is the hymn.
The Savior reigns! Let heaven and nature sing with joy! Let men their songs employ. He does rule the world with truth and grace. And - in today's world - he does make the nations prove the glories of his righteousness.
Joy to the world!