That got me thinking about how many other countries' constitutions have a religious dimension. The "religiosity" of a country's basic law, as I discovered, generally tells you more about its political history than about the religious feelings of its present-day population. The American constitution contains no reference to God, unless you count the words "In the year of our Lord..." During the civil war, there was an unsuccessful movement (on the northern side) to insert an explicitly Christian amendment. To many early Americans, it must have felt strange to live in a country which had no established religion, and where the First Amendment made clear there would never be one. But remember, America's founders were keen to distance themselves from the harsh and divisive theocracies of Europe.
Meanwhile many European countries, whose populations are less devout than America's, retain some reference to God or religion in their system or founding charter. Under Britain's unwritten constitution, the monarch is head of the Church of England and guarantor of a different church in Scotland. In Norway, where I have just arrived for a human-rights conference called the Oslo Freedom Forum, there have been some moves to loosen the link between state, church and crown, but the process is incomplete. The country no longer recognises the Lutheran church as the established faith, but it is still officially designated as the "people's church" and the monarch must belong to it. If you have a monarchy whose authority is (however vestigially) spiritual as well as temporal, then you have a political system which is not entirely secular.