Why did Paul Langan write is

Please provide more context! Who is Paul Langan? What is "is" referring to?

For example, you could ask:

* "Why did Paul Langan write his book, 'The Book of Lies'?"

* "Why did Paul Langan write the article about the history of the internet?"

* "Why did Paul Langan write 'is' in that sentence?"

I need more information to understand your question and provide a helpful answer.