Ever since the dawn of Man, biological systematists have searched a consistent, unambiguous and all-encompassing species concept. Just recently, in 1901, Bertrand Russell did, however, reveal that this search is vain and why (by Russell’s paradox). The reason is that such a concept has to include “the kind of kinds”, which Bertrand Russell revealed is paradoxically contradictory.
The old question: what is a species? should therefore rather be formulated as: what is “species”?, and the answer is: the kind of kinds, which Bertrand Russell thus revealed is paradoxically contradictory. “A species” is thus an illusion (behind a paradoxical contradiction).
So, what does this make “a clade”, or “clades”? A group and groups of illusions?