Is it possible to get a pattent/copyright for a theory? If so, how would one go about that?

It is more likely that your best route would be to copyright your written theory.

And how does one do that?

Agreeing with ballengerb1, a patent is only given to machines, design plans for machines or creating anew type of plant... I don't know why.

In any case, check the link General Information Concerning Patents (http://www.uspto.gov/web/offices/pac/doc/general/index.html#patent)

Publish your theory and get the publication copyrighted.

Try this for a start The Learning Page-Getting Started: Copyright (http://memory.loc.gov/learn/start/cpyrt/) Most of this info is on the net so simply Google what you are looking for and you'll be surprised what you get. Be cautious because some Google sights just take you back to the discussions of others. A final word of caution, do not state your theroy here, it will be open to all and your chances of a copy write will disappear.