In this world there are two kinds of people

Tuco (Eli Wallach), coming by the window

There are quite a bunch of quotes and sayings starting with "In this world there are two kinds of people" since one can divide people in whatever two categories he wants. One of the most famous is this one said by Blondie (Clint Eastwood)  in The good, the bad and the ugly : "you see, there are two kinds of people in this world, my friend. Those with loaded guns, and those who dig. You dig". It was like a response near the end of the movie to Tuco (Eli Wallach) quotes categorizing people in two categories like "There are two kinds of people in the world, my friend. Those who have a rope around their neck and those who have the job of doing the cutting" meaning that he is the one deserving the money for risking his life and "There are two kinds of spurs, my friend. Those that come in by the door and those that come in by the window" said when Tuco surprised Blondie by coming by the window instead of the door like his dead teammates.

A different kind of example which is famous among programmers is "There are 10 kinds of people in the world, those who understand binary and those who don't" taking advantage of the fact that 10 in base two system is the number two. With this technique one can go ahead and divide people using the digital representation 10  and meaning any number greater or equal to two. But someone has come up with this genius quotation to put an end to the series :"There are 10 types of people in the world; those who know quaternary, those who mistake it for binary, those who mistake it for ternary, and those who are sick of these jokes".

See you in the next saying.