When we look at reality, we see things and what we comprehend as kinds of things. An ancient question is whether such kinds (of things) “exist”, also expressed as “are real”, or not.
This question early split humanity into the two main branches of approaches called “nominalism”, assuming as an axiom that kinds do not exist, and “realism”, assuming as an axiom that kinds do exist.
This question was solved by Bertrand Russell in 1901, when he demonstrated that realism is inconsistent, ie, ultimately leads to paradox, by what was called Russell’s paradox.
This demonstration preceded Einstein’s understanding that time must be relative to speed in space, and its further development into what is called quantum mechanics. (In Sweden interestingly instead called quantum physics. The approach is thus ambiguous between mechanics and physics.)
However, all along this development, realism never gave up to Russell’s falsification of it, but instead continued to coexist with nominalism as an opposing underflow. It stuck up its head again (I was almost saying “ugly”) during the two World wars in the form of what is called “race biology”, again in the 1960-ies as what is called “cladistics”, and again recently as the notion of “Higgs particle” in what is called “particle physics” (but no, it has not yet created “wave physics”, “particle mechanics” or “wave mechanics”, although the doors to them is open for realism). It even awarded itself the Nobel Prize for nearly finding the “Higgs particle” last year.
This last self-affirmation is actually the problem with realism – it is very nearly true (as a cladist expressed it), but yet totally wrong. It makes it very tempting for realists to cross the unsurmountable boundary between wrong and right by first conflating concepts that marks the difference between them, like real and abstract, and then (obviously) by suggesting that they have almost found empirical evidence for this crossing (ie, for this conceptual conflation). They want it so much that they are willing to almost say that they have proved it empirically.
Realism is thus a struggle to verify that verification is a consistent approach, which obviously still is alive and kicking although Bertrand Russell falsified it more than a century ago with Russell’s paradox, and although quantum mechanics today is taking the rudder in science. The question now is thus not whether realism will succeed or not, but rather when it will look ridiculous to more eyes than mine and my (obviously still few) mates (in which case it will not be awarded with a Nobel Prize).
Fact is thus that kinds (of things) do not exist. There are indeed clusters of similar things, but the axiom that kinds are real (ie, realism) is wrong (ie, ultimately paradoxically contradictory). It does thus not matter how long we try, never will we find a consistent classification. And, this is true independently of whether biodiversity has originated by evolution or not, and independently of whether it means that reality is unambiguously understandable or not. It actually undermines all considerations about the reality we see and discuss.