When the Bible speaks of “the world,” it isn’t speaking of planet Earth as much as it’s speaking of a culture—the culture of the world. The Bible says, “For all that is in the world—the lust of the flesh, the lust of the eyes, and the pride of life—is not of the Father but is of the world” (1 John 2:16 NKJV).
Another version puts the same verse this way: “Practically everything that goes on in the world—wanting your own way, wanting everything for yourself, wanting to appear important—has nothing to do with the Father. It just isolates you from him” (MSG).
You can almost take every sin you’ve ever committed and put it in one of three categories: (1) the lust of the flesh, which is physical desire, (2) the lust of the eyes, that which we see and want, or (3) the pride of life.
Those were the very sins that trapped Eve in the Garden of Eden: “So when the woman saw that the tree was good for food, that it was pleasant to the eyes, and a tree desirable to make one wise, she took of its fruit and ate” (Genesis 3:6 NKJV). She saw the fruit was “good for food” (the lust of the flesh), it was “pleasant to the eyes” (the lust of the eyes), and “desirable to make one wise” (the pride of life). We fall into those sins as well.
When the apostle Paul said, “Do not be conformed to this world” (Romans 12:2 NKJV), he was effectively saying, “Christian, don’t try to be something you really are not.” To put it in modern vernacular, don’t be a poser. Don’t act like you’re not a believer when in reality you are. Don’t be conformed to this world.