What's the most intriguing philosophical idea you've heard of?

[TheDarkElf]

For me one that I've been thinking about recently is the concept that we are in a dream and nothing is real.

 

[QUEENOFCHICKENS]

everybody around you knows something that you dont
xD

 

[Notorious Bum]

If you replace all of the parts in a car for example, is it still the same car?

 

[Digitus]

I dreamed that this was all a dream, a virtual reality so that we would not discover the truth, the rest I remember is seeing someone with many arms and a lot of computers, writing the reports, controlling us, lying to us, the dream continued with talking to me about the false reality, the truth I have kept that dream in my mind, thinking about it.

 

[Ketsui/Kezzai]

The idea that not everyone perceives everything the same way