Do not love the world nor things in the world. If anyone loves the world, the love of the Father is not in him. 16 Because all the things in the world, the lust of the flesh and the lust of the eyes and the pride of life, are not from the Father but are from the world. 17 And the world is passing away and its lusts, but the one who does the will of the Father remains forever.
This passage begins the recurring theme of love and its import to the Christian. This time, love is focused in a negative way, as in what not to love. The world here stands for those things not from God. This can be seen in the terse explanation that love of the world precludes love from God.
Note how that was worded: love of the world, in other words the love one has for the world, precludes love from God, that is the love instantiated in the person of Christ. One can either love the world or be saved. John does not allow room for gray, he sees this in simple black and white.
