> Most concepts in biology break down on the borderline cases
Most concepts break down on borderline cases, within and without biology. Those motivated will abuse this to argue that those concepts don't meaningfully exist at all.
Most concepts break down on borderline cases, within and without biology. Those motivated will abuse this to argue that those concepts don't meaningfully exist at all.
Take our color perception as an obvious example: We clearly see different types of color, despite us being unsure at the thresholds in between, and the actual electromagnetic radiation of visible light being a continuous wavelength range.
That is just a fundamental limit of our reasoning. We mentally make models of the world to make sense of it. These models have to be of less complexity than reality, ergo they have to cluster perceptions, ergo we have to categorize.
And even when the attributes are discrete, phenomena tend to be highly combinatorial.
Leaving lots of room for new combinations to be discovered that will upset our taxonomies.
The definition of steel is pretty hard-edged. A polymer of C, H, and O isn't steel.
The definition of a quasar is similar. There are "maybe quasars", but that's from lack of data, not lack of definition clarity.
A circle is pretty exactingly defined. Mathematicians aren't fuzzy on that.