Answer not a fool according to his folly,
lest thou also be like unto him.
Answer a fool according to his folly,
lest he be wise in his own conceit.
This can seem confusing and contradictory, but is really a play on words. When you consider the following verses defining what a fool is, it unlocks the meaning:
The fear of the LORD is the beginning of wisdom:
and the knowledge of the holy is understanding.
The fool hath said in his heart, There is no God.
They are corrupt, they have done abominable works,
there is none that doeth good.
The beginning of wisdom, or the starting point of any reasoning, is the reverence of God.
Someone who doesn’t reverence God, has the wrong starting point. No matter eloquent an argument they might make, they will never reach the right conclusion because their starting point was wrong. This is why they are a fool who say there is no God, and why any arguments they make are a folly.
Man’s wisdom is limited and faulty, and any reasoning that does not have God and God’s word as a starting point (a biblical worldview) is self deluded conceit and will always go awry.
If you let a fool set the rules for the debate, such as “you can’t use scripture to support your argument”, you have already lost the debate and you are only joining the fool in his folly.
Instead of joining the fool in their folly, we need use God’s word to expose the conceit of the fool embedded within their folly.
For example, if you get into a debate on “why sodomy is wrong”, and you allow the fool to set the terms of the debate, the fool will always have some “exception” to every argument you throw at him. For example if you try to say that it is abusive for sodomites to adopt children, then they will pull out examples of very nice, respectable, peaceable, and “moral” sodomites who have raised perfectly normal children (they will of course refuse to acknowledge any and all examples to the contrary).
While sodomy is indeed harmful to families, children, health, and society these things will not do anything to change anyone’s hearts or position.
Instead of trying to explain why sodomy is wrong using man’s limited wisdom, we need to stand on the truth and use God’s word to answer the fool — that sodomy is wrong because God has said it is wrong. This reveals the conceit in the fool’s folly, that the fool thinks he doesn’t need God to know right from wrong.