[Grammar] itself or in itself?

[NORINET]

Which one is correct?
Semiotics is not a discipline itself or Semiotics is not a discipline in itself?

 

[mayita1usa]

Which one is correct?
Semiotics is not a discipline itself or Semiotics is not a discipline in itself?

I would say it one of these two ways (but I haven't got time to work out why, they just sound better!):

1 - Semiotics itself is not a discipline.
2 - Semiotics is not a discipline in and of itself.

The second one is an idiomatic expression.