I know, but I do not know all

I may know darkness like a long known and familiar friend, I may be comfortable with the existence of such old friend, but that doesn’t mean I know every single thing there is to know of the darkness, yet I know the depth in which it can reach simply through experiencing darkness itself. One can know the depth of the ocean without knowing all that lives there, i too know the depth of darkness without knowing all that dwells in it.