Hey, guys, this may be a dumb question, but let's say that you were inside a small chinese restaurant in NYC at night. The streets are fairly dark, (as dark as they can be in nyc). There are lights on inside the restaurant. Could you look out the window and see people walking?
If the people were close enough to the glass, probably, or if they were walking right under a streetlight. But you wouldn't see much at a distance or in the shadows. You can probably simulate this pretty well wherever you're living - you don't need to be in a Chinese restaurant or in NYC, just anywhere with lights on inside and minimal lighting outside.
One other thing to try (if you haven't already) is to put your face to the glass and cup your hands around your eyes. Then you could see more detail in shadows if the character needs to. But anyone lurking would have a pretty good idea of what's going on.
I am not sure why I thought that the title of this thread was a philosophical question when I first stumbled upon it as something I should read. Still have a lot to learn about what kind of questions get posed here I guess.
It would depend on how bright it is outside, how bright it is inside, how close the people inside are to the windows, and what kind of glass it's made out of. Even if it's fairly dark outside, and fairly bright inside and you can't see anything outside, if you sit close enough to the window you'll be able to see through the window when your own shadow is cast on it, blocking the bright inside lights.