whenever you are addressing anyone directly with “you” pronouns, the way you’re talking is called “second person”

but what if you are talking to a wall?

the wall isn’t a person.

so you cannot be addressing it in second person, that doesn’t make sense.

so what name do we use for this form of address?

“second wall” also would not make sense.

Because that would make you the first wall.

And you are not a wall.

…however, you are likely surrounded by other walls.

and the wall to whom you are talking must be differentiated from those walls, which you are not addressing directly.

and a room usually has one wall behind your back, and one to each side of you

so there are three to count before you reach the one you’re speaking to

and thus.

in any work of fiction

a character who’s alone in a room literally talking to a wall (his soliloquy clearly intended for no one but the audience)

is addressing the fourth wall.