That quote running below the image at the head of this article comes from the opening minute of this particular developer diary. It's said by Christophe Carrier, the Lead Level Designer at Arkane Studios for Dishonored.
In fact, that line is really the core experience that the Dishonored marketing campaign is touting the most for potential players.
The game is all about freedom and choice. See something, get to it. You can open all doors, posses all characters, kill everyone or kill no one. That's the nature of Dishonored, or, supposedly, the nature Arkane Studios is intending to produce.
Dig the developer's diary here.
Dishonored is set to release for the Xbox 360, PlayStation 3 and PC platforms on October 9th of this year.