Best word for "Dr. Einstein, <blank> of the theory of Special Relativity."

What is the best word to describe the creator of a scientific theory? As in:

Einstein was the _____ of the theory of Special Relativity.

Creator, author, originator, and inventor are possibilities, but which is the most appropriate/accepted term?

EDIT:

“Father” seems to be the best fit for the example I gave, but is less apt for theories not as widely recognized as relativity or evolution. What would be the term for a less renowned scientist who has proposed a more controversial theory?

Einstein was the "father" of the theory of Special Relativity.

Charles Darwin was the father of the theory of natural selection.

Most of the professors I know wouldn't refer to themselves as inventors, creators, or any such word denoting actual creation of a physical phenomenon. They see themselves as founders rather than creators; they don't invent the rules, they merely describe them. For that reason, I would consider the following over a synonym for "create." Note that I think a verb would probably work better than a noun, but given the placement of the blank and the words you provided...

Founder, pioneer, presenter, developer.

But when they are described by others who don't reflect the modesty of the founders themselves, inventor is the word I see most often.