This is a famous card “trick”. It’s actually not really a trick at all but when I learned about this “trick”, it was the first time that I realized that the human brain isn’t all it’s made out to be.
Here’s the “trick”:
If I tell you that these four cards belong to a deck where if there’s a vowel on one side, then the other side is an even number, which two cards would you flip over to see if I was right?
I’ll explain tomorrow.