People. You can't live with them, you can't move to a desert island to escape them.
The early Christians banded together to form small local communities where they could worship together and support each other (Christianity wasn't the most popular religion around). Paul sees belief in Christ as a group effort. Christians need to work together as a team to keep things going. Sure, sometimes there would be problems, but the good times would outweigh the bad. Fingers crossed.
Questions About Community
Why do people want to live in communities? Do the benefits of being with like-minded people make up for the tough times?
Paul says he's never been to see the Colossians. How does he know so much about their community?
Do you think the image of a human body fits for a community? Why or why not?