What Defines You as a Christian?

My good friend Jason has begun blogging at Personal Theology. Today he asks the following questions.

What above all else characterizes a Christian? The Republican party? Opposition to abortion and gay marriage? Is it creationism vs. evolution(ism)? Is it morality? The 10 commandments? The location of the 10 commandments in public places? Is it boycotts of offensive/immoral movies? Is it 7 steps to how to live life to its fullest? Is it don't drink, don't smoke, don't chew (or go with girls who do)? If one were to take a poll of non-Christians—heck, if a poll were taken of Christians themselves—what would be said to be the defining characteristic of a Christian? What would be that sine qua non of Christianity?

See the full post for Jason's answer.