Here's my test: You have 30 seconds. Don't read the article and don't look anything up. Write one sentence articulating a secular purpose for having "In God We Trust" on the money. Do the best you can — that is, be
ADDED: I will read all the comments later today and pick some winners, but after reading a few, I feel like saying that the requirement that a law have a secular purpose can be diminished to nothing if you accept the proposition that there is a secular purpose for religion. Government can always say it is using religion to mollify/control/improve people for worldly ends. The argument would be that as long as religion is the means and not the end, it's a secular purpose. Note that complete atheists could embrace this kind of religion (and I assume they have throughout history all over the world).
CORRECTION: The original post said "on" where it should have said "against." That was confusing, and I'm very sorry. It makes no sense — perhaps you noticed — to articulate the FFR side, which is there is NO secular purpose. The idea is to come up with a secular purpose, and I wanted you to do your best at that, even if you'd prefer to see FFR win this.