What is an Incorporation Theory ?

Answer 1

Three common legal uses of the word.

First, incorporation can refer to the concept of creating an artificial business entity (a 'corporation') which exists independently and has some but not all rights of an actual person.

Second, there is "incorporation by reference" which allows the contents of one document to be included in another. The later document references the earlier one, and basically says: 'anything that was in that one, treat this one as if it said the same thing'. It's a convenient way to copy-and-paste with legal papers.

The third legal use of the term relates to the Selective Incorporation doctrine in constitutional law. Most of the Bill of Rights applied only as limits against the federal government. However, through the 14th Amendment, most of those same protections and restrictions were applied (incorporated) against the states. Selective Incorporation says only some (most) of those were applied, as opposed to Total Incorporation.

I'm sure there are other uses of the term as well.

Answer 2

It means some doctrine or concept is incorporated in some other doctrine or concept.