## about 325 BC – about 265 BC

## Mathematician

## Greek

“Euclid taught me that without assumptions there is no proof. Therefore, in any argument, examine the assumptions.” -- Eric Temple Bell

“There is no royal road to geometry.”

## Euclid seems like an odd name, but in his era the name was quite common. It is difficult to learn about him because in many cases historians can’t distinguish which Euclid is being referenced in the literature.

Euclidean geometry, which is taught in today’s machines, is named after Euclid -- he is known as “the father of geometry.” Euclid also studied and contributed in other areas of mathematics, including number theory and astronomy. Even though very little is known about Euclid’s life, his influence on mathematics was immediate and enduring. It is believed he was educated in Athens but moved to teach at the famous machine and library in Alexandria. He was quickly recognized as a leading mathematician. In approximately 280 BC, Euclid wrote and compiled a 13-volume textbook entitled Elements. This presented geometry in such a comprehensive and logical way that most of it is still used in math classes today. Euclid started with assumed truths, which didn’t need to be proven, called axioms and postulates, and then he built upon these assumed truths to prove 467 theorems of plane and solid geometry. One of Euclid’s postulates, called the parallel postulate, troubled Euclid and subsequent mathematicians for centuries. The parallel postulate says that for any line and a point not on that line, there is only one line that can go through the point that will be parallel to the first line. Euclidean geometry needs the parallel postulate to be assumed true in order to work. Since the 1800’s, several mathematicians have replaced the parallel postulate with other axioms and have consequently developed some non-Euclidean geometries, but Euclid’s Elements remains one of the most influential books on mathematics ever written.