> Even believing the son of god is not universal among Christians. It is nearly universal--universal enough to be useful. If someone says they are a Christian,

> Even believing the son of god is not universal among Christians. It is nearly universal--universal enough to be useful. If someone says they are a Christian, absent any other knowledge, you can be very confident that they mean that Jesus Christ is the son of God. Obviously not 100% confident, but confident enough to proceed with that assumption in most cases. I could say that a car mechanic, a pilot, and a web developer are all skilled trades. That doesn't make the term skilled trade meaningless, it just makes it less specific. "Christian" is a very broad classifier and it is about as useful as any other broad classifier. It lacks specifics, but language is recursive--I can add as many extra identifiers as I like, e.g., Protestant Christian, Roman Catholic Christian, and Orthodox Christian.