Dave Miller, who has an MS in biology and is contributing to research on prolidase deficiency in humans, writes us to say:
I have a running debate with a couple of coworkers about how (in their opinion) stupid biological taxonomy is because taxonomists don’t simply choose a species concept and stick with it.
Apparently, his co-workers are not trained biologists (except for undergrad degrees) and complaining about taxonomy does ease their way through a dreary day, no doubt. 
Dave goes on to say,
This got me thinking about why biological taxonomy is so much more complicated than chemical, geological or physical taxonomy. Indeed, chemists don’t have debates over whether atoms with 6 protons ought to be called “Carbon” simply because some of them have 6 neutrons, others 7 and yet others 8. The fact that they all have 6 protons makes it “Carbon.” What makes this so much simpler?
It dawned on me that chemistry, physics, geology, etc are all fields that study objects that are static by their very nature. There is no principle in chemistry that causes the laws of gravity to change over time in an effort to find some ideal level of gravitation. Gravity is what it is: we are merely tasked with describing it.
Life, however, is distinguised from non-life in that life is decided non-static. Indeed, it may be said of life that varibility is a defining quality. When a human cell undergoes meiosis to form an egg or sperm cell, the four daughter cells have a a total of 2^23 (that’s 2 raised to the 23 power) possible number of chromosomal arrangements. A cactus with 500 chromosomes has a total of 2^500 possible arrangements (and this doesn’t even consider cross-over events!). In short, that fact that we resemble our parents to a great degree ought to amaze us.
In short, much of biology is based on probabilistic principles rather than the laws of the physical sciences. Predicting the outcome of biological experiments is often like predicting what cards your oponents are holding in a poker match. There are people who have developed skills that enable them to be better at it than others but, in the end, no one can know the result with the same certaintity of a chemical reaction unless they have rigged the game in some way (by either stacking the deck or observing the deal).The end of the tale is this: pythagoreanism is as applicable to biology as to the physical sciences so long as one is content to remain in the realm of probability and be stuck in a casino rather than a chemistry lab.
Hmmm. The species concept does sometimes seem to be an artificial order imposed on a more messy reality. But is there a better way of doing it? Any thoughts?
Anyway, while we are here: Once life gets started, it can be hard to cure. I have known old people walking around with conditions that should have killed them, at least if you go by the textbooks. Or the coma victim whose brain completely rewired itself over a period of years after a massive injury, whereupon he woke up. Similarly, Viennese psychiatrist Viktor Frankl, an Auschwitz survivor, recalled that camp inmates survived for long periods with far less food than the textbooks insisted was required for life. The trouble and ingenuity to which humans go to battle entropy and preserve our lives, even when old and wretched, is amazing. And definitely not calculable or orderly.