Why does the bible say in John 3:16 that "For God so loved the world" but 1 John 2:15 says "Love not the world". If God Himself loved the world, why shouldn't we love the world?
The Greek word used in both verses is ‘kosmos’ but, according to the context in which it is used, it has different meanings. The following explanation is from a Protestant perspective.
Kosmos, or world, can mean the physical world, this planet; the present order of things; the secular world; the human race external to the Jewish nation; the heathen world; the world external to the Christian church. (Source: William D. Mounce Interlinear (for the rest of us), page 581)
John 3:16 is about God’s love for the people he created. Here is a comment from the New International Version Study Bible on the meaning of this verse:
The great truth that motivated God’s plan of salvation.
That “great truth” is linked to 2 Peter 3:9 where it says that God is patient with us because he does not want anyone to perish, but everyone to come to repentance. That is the sense in which God loves the world.
When we turn to 1 John 2:15 we discover the context in which the word “world” is used has to do with the realm of sin that influences the people who have rejected God. Verse 16 explains:
For everything in the world – the craving of sinful man, the lust of his eyes and the boasting of what he has and does – comes not from the Father but from the world.
The New International Version Study Bible makes this comment:
The World – Not the world of people (John 3:16) or the created world (John 17:24), but the world, or realm, of sin which is controlled by Satan and organised against God and righteousness.
So when John says not to love the world, he is speaking about the world, or realm, of sin. Those who follow Christ must renounce worldly sins and pleasures. At the same time, Jesus tells us to love our neighbour as ourself, even to loving those who persecute us by forgiving them and praying for them.
The "world" that John 3:16 is speaking of is the people, not the behavior. Look at the whole context.
[John 3:14-21 NKJV] 14 "And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, 15 "that whoever believes in Him should not perish but have eternal life. 16 "For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. 17 "For God did not send His Son into the world to condemn the world, but that the world through Him might be saved. 18 "He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God. 19 "And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil. 20 "For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed. 21 "But he who does the truth comes to the light, that his deeds may be clearly seen, that they have been done in God."
Jesus is telling us that He is going to be lifted up, and those that desire to do the deeds of truth will come to the light, because they believe on Him. This requires sacrifice of the "world" in the sense of the desires of this world.
[Mark 8:36 KJV] 36 For what shall it profit a man, if he shall gain the whole world, and lose his own soul?
He tells us here, that we must seek not after the world but the desires of God. Paul and James tell us the same thing John does in 1 Jo 2 (and 4)
[Romans 12:2 KJV] 2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what [is] that good, and acceptable, and perfect, will of God.
[James 4:4 KJV] 4 Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God.
[1 John 4:3-5 KJV] 3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that [spirit] of antichrist, whereof ye have heard that it should come; and even now already is it in the world. 4 Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world. 5 They are of the world: therefore speak they of the world, and the world heareth them.
A love of the world fills our mind with desires for the world, and not desires for the living word. Christ came to free us from the bondage of the world, and did so because He loved the people of the world. But He does not love the world and its wicked desires.
[Psalm 7:11 KJV] 11 God judgeth the righteous, and God is angry [with the wicked] every day.
"For God so loved the world". What does it mean? It could mean God loves everyone but then why does John17v2 talk about Jesus only giving eternal life to those you have given Him? It could mean God loves worldly people which e.g. the disciples were when Jesus first met with them. "The true light which enlightens everyone" here in John 1v9 it sounds like God loving everyone, but,say, light falls on a house but no one is given the grace to get up and open the curtains then the light will not enter it. What if God speaks of His love not, for all people, but about His love for some people to all people? What if by making some not born again God denies them the response to His love which would enable them to receive that love? In this situation it would be true to say God is causing His light to shine in their direction and they are not receiving it. But that by itself would not be the whole truth because it would be failing to mention why love was not being received.