There are three important classes of intellectual property which are often confusing. Society grants a limited monopoly on each intellectual property because it serves a specific public interest.

Trademark

• Superman can be a trademark of Clark Kent.
• However, Clark Kent cannot be a trademark of Superman.

The mark Superman™ is an chosen public image that stands for a particular individual in this case. Society grants Clark Kent a monopoly on the use of that public image, because there is a public benefit to their avoiding impostors.

Clark Kent is a "secret identity". The public has no vested interest in keeping secrets.

Patent

• Superman might patent X-ray vision.
• However, Kryptonite would be a trade secret.

Superman could patent x-ray vision if he wanted a limited monopoly on producing x-ray vision glasses. But first, he would have to publicly describe how x-ray vision worked in enough detail so that others could reproduce it. Facilitating broad understanding of inventions is a shared public interest.

Kryptonite however, is one of Superman's trade secrets. He cannot apply for a patent in order to keep knowledge of Kryptonite's use from the public. That was never the intention of patents. Inventors require no assistance (and the public has no vested interest) in keeping secrets.

Copyright

• Public stories of Superman are copyrightable.
• Superman's secrets are not.

If Superman wanted to tell the public his life story, he could write it down and claim a copyright on that work. This would allow him exclusive right to publish his work. The term publish comes from the Latin for "make public". Copyright gives the author a limited monopoly to manufacture copies of his work and to distribute those copies to the public. However, to claim this monopoly the author must first make his work available to the public, by depositing copies with the nation's archives.

However, if Superman wishes the story of Krypton and Jor-El to remain private, he cannot use copyright to enforce his wishes. The public has no vested interest in, nor does it grant monopolies to, secrets.