Monopolies over the creations.

Thomas Jefferson's proposal for the Amendment that granted copyright and patents was:

  Art. 9. Monopolies may be allowed to persons for their own productions
  in literature and their own inventions in the arts for a term
  not exceeding — years but for no longer term and no other purpose.

Madison, on the other hand, wrote:

  Monopolies, though in certain cases useful, ought to be granted with caution,
  and guarded with strictness against abuse. The Constitution of the United
  States has limited them to two cases--the authors of books, and of useful
  inventions (...)