by Carl Pierer
It is necessary that two men have the same number of hair, gold, and others.[i]
This meme is taken from a scene in the Cohen brother's 1998 comedy “The Big Lebowski”. During a game of bowling, Walter, in the picture, gets annoyed at the other characters constantly overstepping the line. Drawing a gun, he asks: “Am I the only around here who gives a shit about rules?”[ii]
Considering that there are roughly 7 billion people on earth, a positive answer seems highly unlikely. But it is possible to do better. We can know with certainty, i.e. prove, that the creator of the meme is not the only one. This is a simple and straightforward application of a fascinating, intuitive and yet powerful mathematical principle. It is usually called “pigeonhole principle” (for reasons to be explained below) or “Dirichlet's principle”.
***
The German mathematician Gustav Lejeune Dirichlet was born in 1805 in Düren, a small town near Aachen. Although Dirichlet was no child prodigy, his love for mathematics and studies in general became apparent early in his life. His parents had him destined for the career of a merchant, but upon his insisting to attend the Gymnasium (secondary school), they sent him to Bonn, at the age of 12. After only two years, he transferred to a Gymnasium in Cologne, where he studied mathematics with Georg Simon Ohm (1789-1854), who is famous for his discovery of Ohm's Law. Dirichlet left this school after only one year, with a leaving certificate in his pocket but without an Abitur, which would cause him some troubles later in his life. At that time, students were required to be able to carry a conversation in Latin to pass the Abitur examination. With only three years of secondary education, Dirichlet could not comply with this crucial requirement. However, Dirichlet was fortunate that no Abitur was required to study mathematics.