I'd like to share a few of Sye Ten Bruggencate's analogies.
The first one is one he uses a lot that he credits to Doug Wilson. Imagine you have a bottle of Dr Pepper and a bottle of Sprite and you shake them both up. The result is a chemical reaction that causes both of them to fizz and overflow. Which chemical reaction is true? Of course the question doesn't make sense because you don't get truth from chemical reactions. In this case you just get fizz. Likewise with evolution - it doesn't give us truth - it just gives us brain fizz. How do you get truth without God? The answer is you don't - you just get brain fizz from the chemical reactions in ones mind.
Another analogy I liked explains why unbelievers don't like the presuppositional approach Sye uses.
Imagine a person is building a brick wall and they have just finished laying the final brick. It's a large wall and you look up at them and point out to them that the final brick is slightly crooked. The guy isn't too upset because it's just one brick and it's easy to fix. They thank you for your help.
Imagine though if the person building the wall is laying the final brick and you point out to them that the bottom layer of bricks are all crooked and seriously out of place. The person will likely get angry with you and deny that there is a problem because if he admits there is a problem with the foundation it means that the whole wall is no good and to fix the problem he'll have to tear the whole wall down and start again from scratch.
In the presuppostional approach we aren't just pointing out to them that there is a God shaped hole in their heart that can be fixed by tacking Jesus onto their life with a very minor adjustment. We are pointing out that their whole worldview is wrong from the foundation up and they need to repent and change their whole thinking from them being the Lord of their own reasoning to making Jesus the Lord of their reasoning.
An analogy that Sye uses to illustrate that knowledge is justified true belief is the speed limit analogy. Imagine if I said that the speed limit here is 50km/h but I'm not sure. Do I know this? Clearly I don't know it. I may even be correct in my assumption, but my belief is not justified as it may not be true. Anyway in order to know things for sure we'd have to know everything (be omniscient) otherwise something we think we know could be contradicted by something we don't yet know which would expose our false beliefs. So in order to know things for sure we either need to be God or have revelation from God. Otherwise how would we know that everything isn't just an illusion or some kind of Matrix world or computer SIM game world?
Another analogy Sye used is in relation to the idea that truth is whatever works pragmatically. Just because something works doesn't make it true or right. Imagine a father who is getting absolutely fed up with his daughter making too much noise. The father could kill his daughter, and this would work in terms of stopping the noise, but clearly it would not be right.