{Not of the world} (ouk ek tou kosmou). They are "in the
world" (en t(9369) kosm(9369), verse  13 ) still and Christ sends them
"into the world" (eis ton kosmon, verse  18 ), but they must
not be like the world nor get their spirit, standards, and
message "out of the world," else they can do the world no good.
These verses ( 14-19 ) picture the Master's ideal for believers
and go far towards explaining the failure of Christians in
winning the world to Christ. Too often the world fails to see the
difference or the gain by the change.