Is a term used to describe a nihilist
or alternatively (and in my opinion unfairly) an atheist
. The idea is that a cathedral of one, is someone who derives all meaning from himself. In the case of a nihilist this makes sense, because what is the point of a relationship, if nothing has meaning
It's not really fair when it's applied to an atheist, because atheists, unlike nihilists, can find meaning in life. Therefore, they are not necessarily withdrawn.
Recommended Reading on this subject:
The Stranger by, Albert Camus