Where is the black?

[Parki]

When I experience something I also experience it's opposite.
for example: when there is lenght there is right and left, when there is white there is black

but what if I my experience would be a white screen and that's it
where is the black?

ps no idea if it's understandable but I can't go closer(well at least now, maybe I could explain it better in the future)