Lisa, the Grace Kelly character in Rear Window:
LISA: All day long I’ve been trying to concentrate on my work.
JEFFERIES: thinking about Thorwald ?
Just as we’re wandering off thinking about the James Stewart character (is he off his rocker spying on folks ?), or how the set looks realistic
and artificial at the same time, or musing about how the voyeurism is a step back to the best in silent films, that we can watch people acting, from a distance, or how much like an iris the realistically-motivated cache imitating the tele-objective lens Stewart is using,
Delicious Devil (1919)
or…a character comes in and warns us to re-focus our attention on the main plot.
I know this is supposed to be proof that Hollywood filmmaking just packs in clues to guide the viewer through plot lines; I’m tempted to think that it can also be explained outside of the classical style paradigm: that it’s a way not to guide or attention prior to its wandering, but after it. In other words, the classical style tries to guide us back to the plot — but like laws prove crime exists, by so doing it merely proves that there’s way much more to look at (clues prove the distraction of the audience). Sometimes it makes an effort to upbraid us and takes us to task and guide us back to what we could be doing (following the plot), but even more often it lets us wander deliciously, from distraction to distraction–while we’re following the plot, like Grace Kelly, only we can concentrate on several things at once.
LT. DOYLE: Your logic is backward
Maybe. But even the characters are engaged in several pursuits at once: the Stewart and Kelly characters, for instance, trying to hit their high romantic note by….dreaming up murder plot. What’s more incidental ? The murder, or their desire ? 
The plot, or the light ? And who’s to say ?
