If you have been a Christian for any amount of time you have likely come across the phrase, "In the world, but not of the world." Growing up in a fundamentalist Christian school that meant that we literally were not to look like the world. To show an example of this I can remember a chapel speaker bringing up students that in his mind exemplified this. If you were a female this meant you were wearing a skirt that at minimum went to the bottom of your knee cap and wore some type of blouse that revealed a minimum amount of your arm. If you were a guy this meant that you wore some slacks with a button down shirt tucked in with a belt, and of course you had a neat hair cut and no facial hair. As you can guess, I was always looked down and judged at this school as I do not fit that description easily.
This popular slogan comes from John 17:14-19:
I have given them your word, and the world has hated them because they are not of the world, just as I am not of the world. I do not ask that you take them out of the world, but that you keep them from the evil one. They are not of the world, just as I am not of the world. Sanctify them in the truth; your word is truth. As you sent me into the world, so I have sent them into the world. And for their sake I consecrate myself, that they also may be sanctified in truth.
What does "In the World, but Not of the World," not mean?
I will go ahead and flat out tell you with full conviction that my fundamentalist Christian school had this dead wrong. For them it was all about external rules and regulations that would physically make you look different, but this is not what Jesus is calling us to. Yes, we can all agree that Jesus does not want us to be "of the world," as he himself is not of the world; but Jesus does want us to be "in the world," as that is where he himself is sending us.
What does "In the World, but Not of the World," mean?
I agree with David Mathis here who says, "Maybe it would serve us better — at least in light of John 17 — to revise the popular phrase “in, but not of” in this way: “not of, but sent into.” The beginning place is being “not of the world,” and the movement is toward being “sent into” the world. The accent falls on being sent, with a mission, to the world — not being mainly on a mission to disassociate from this world."
This means that as we are "in, but not of" the world we should spend time with sinners. We should have them over for dinner. We should redeem secular holidays such as Halloween. We should attend their parties, and throw the best parties as we have something to truly celebrate. So, as Christians we are not of the world, but we are sent into the world to make disciples of all people.