How do you know a Christian? Is there a way to tell who is and who isn’t? Do you quiz them on their beliefs to see how well they line up with the Nicene Creed? Do you ask them if they’ve invited Jesus into their hearts?
One answer is to check their behavior. If becoming united to Christ changes us, then one should expect to see those changes lived out in everyday life. A number of the Church Fathers suggested a test like this one, though the specific change they were looking for may come as a surprise…