Kant's ding-an-sich or noumena were roundly criticized by Fichte, Hegel, and other near contemporaries as incomprehensible, meaningless, or at least very unsatisfactory. How can we "know" or talk about the existence of an absolute "unknown" or "unknowable" things. Yet they do seem to have a necessary and positive value in Kant's system, an internal limit to certainties.
Have any philosophers since compared Kantian noumena to the functions of the empty set? Especially in the context of ordered sets. Perhaps this is only a very superficial notion. I have little grasp of set theory, so it is hard for me to carry the idea any further. From what I do know, both concepts seem to be regulative principles that remain ontologically controversial in similar ways.Is there anything more to it?