One way to find out if a worldview is false is to apply it to itself. For example, when your friend says there’s no such thing as absolute truth, you may want to ask him if that’s absolutely true.
Deepak Chopra, very popular for being a self-proclaimed spiritual guru, found this out the hard way. Check it out:
When you apply a false worldview to itself, it fails.
Here’s another example. Once, a friend said he wanted to read a book arguing in favor of the philosophical belief that we can never really know anything for sure. I simply asked him what the point of reading the book was, then. How can the author know for sure if he’s right? TH!NK: Even if it was true, we could never know for sure!
For a biblical view of this very thing, consider these verses in Proverbs. They set the standard for Christian apologetics.
Answer not a fool according to his folly, lest you be like him yourself. [Proverbs 26:4 ESV]
When answering a fool (as God calls him), do not sink to his level or compromise according to his own worldview or you will engage in the same behavior i.e. name calling, compromising on theistic evolution, agreeing not to use the Bible in your responses, etc.
Answer a fool according to his folly, lest he be wise in his own eyes. [Proverbs 26:5 ESV]
Hold up the fool’s worldview in front of him so he may see the error in his own belief. Apply his worldview to itself to see if it holds up. It never does.