It is not simply Paul who says it. Our covenant God says through the apostle that the world is a crooked and perverse generation. This He says in contrast to the believers, whom He calls light. For in Philippians 2:15 He declares through Paul, "That ye may be blameless and harmless, the sons of God, without rebuke in the midst of a crooked and perverse nation, among whom ye shine as lights in the world." That word "nation" is better translated as "generation."
Now, surely, we can see the crookedness and perversity of the world today. Sin is developing rapidly. Children today boldly commit crimes which older people did not in the past dare to do. And there are so many sins today that are approved, and defended as entertainment for man. Sins which Scripture clearly condemns and which even unbelievers do not want (not because they love God but because these crimes hurt mankind) are nevertheless what thrill men in movies and story books.
What an awesome calling then our God presents through Paul. The unbelievers are a crooked and perverse generation; and the believers are lights in the world. Those words "ye shine" are better translated as "shine ye." We have here an exhortation to manifest our new principle of spiritual life and to fight against our flesh, which also belongs to that crooked and perverse generation.
We have the calling to reveal by word and deed that spiritually we have been changed so remarkably by our covenant God. Jesus said that in Matthew 5:16 in these words: "Let your light so shine before men, that they may see your good works and glorify your Father which is in heaven." In verse 14 He had also stated, "Ye are the light of the world. A city that is set on an hill cannot be hid."
How about it? Do men see your salvation? Are you working it out? Do you look spiritually different to the world? Or do the unbelievers think you are one of them? Our calling is to glorify God by a sinless walk and by fleeing from crookedness and perversity.
Read: Matthew 5:1-16 .
… believers should learn to forget the wrongs that have been done them,—that they should not, when injured, break out into hatred or ill-will, or wish to commit an injury on their part,—but that, the more the obstinacy and rage of wicked men was excited and inflamed, they should be the more fully disposed to exercise patience. – Calvin’s Commentary (Luke 6:29-30)