The link was direct when I tried it. However, to answer your question, it is a c...

cschmidt on Nov 28, 2012 | parent | context | favorite | on: Advice to a Young Mathematician [pdf]

The link was direct when I tried it. However, to answer your question, it is a chapter from The Princeton Companion to Mathematics. An amazing work covering much of mathematics.

http://www.amazon.com/Princeton-Companion-Mathematics-Timoth...