Ceteris paribus! Which bus is that?

My brush with formal economics has finally started. I always wondered what the mathematical equivalent for ceteris paribus is. It turns out to be apna high school ka partial derivative. Ceteris paribus, for the uninitiated is a much used term in economics denoting, "all other things remaining the same."

Next time you hear somebody tell ceteris paribus, turn back and ask him what happens if the situation is mutatis mutandis. Which is actually the usual case. Now I wonder about the math tools for that!