Maxwell's Demon - Information is power...

[eppie]

... thought experiment proposed by Scottish physicist James Clerk Maxwell ...

I believe the point at the time was that the demon still could not violate the 2nd law because it would require some sort of radiation different than what is in the rest of the system in order to see the molecules and the energy level of whatever light source was used would exceed the entrophy lost by the sorting.

Indeed it was.
@KAndrathe;
read the book 'decoding the universe from Charles Seife
(ISBN 978-0-14-303839-9)
It handles about this topic, of information/energy 'duality'.