You do have your trusty bow, however, with seven different types of arrows. You can use water arrows to extinguish torches and wipe away bloodstains, moss arrows to lay a path upon which you can walk without being heard, and noisemaker arrows to distract guards that just won't turn around. Sure, you have regular arrows as well, and a well placed bolt will remove an enemy. You'd better not miss, because a guard with an arrow in his arm makes a hell of a lot of noise. Speaking of the guards, the enemy AI you encounter is smarter than the proverbial average bear.
Guards pay close attention to their surroundings and take notice the moment anything is awry.
Bloodstains on the carpet, a tiny bit of noise, or the slightest bit of movement in the shadows will send the guards investigating. If you hide, they may return to their normal business. If their suspicions are confirmed, all hell breaks loose. Since this is a time when instant communications didn't exist, guards are only able to summon other guards that are within earshot. Since this is a first-person game, everyone pays close attention to the graphical engine.