There’s a battle raging in biological systematics between those that assume that kinds are real and those that assume they aren’t (ie, about whether kinds are only mental constructs or not).
Those that assume kinds are real are searching for the tree of life (called “cladists”), while those that assume they aren’t instead organize biological organisms in the Linnean system (called “taxonomists”, and if they consider evolution, called “evolutionary taxonomists”).
The problem for cladists is that their assumption logically ends in paradoxical contradiction (as Bertrand Russell demonstrated in 1901), while the problem for taxonomists is that their assumption logically ends in ambiguity (ie, that there are several consistent taxonomies). These problems are actually, however, just two aspects of one and the same problem, that is, Russell’s paradox. They just approach this end point from its two opposite directions.
This battle is thus actually a dance around the empty middle. Never will it stop. Never will anyone find the tree of life nor only a single consistent taxonomy. The battle is thus doomed to rotate around the empty middle forever.
My wonder is how anyone can find any reason to participate in such a meaningless occupation. But, I guess the answer is the same as for all extremes, that is, the wish to believe in something. The problem is that believers can’t understand the fundamental problem with belief.
Another contribution to understanding of conceptualization http://menvall.wordpress.com/