Aristotle
Can living things be put in order?
That time, that place
The Lyceum in Athens. Aristotle had been Plato's student, but he looked the other way. His teacher pointed beyond the visible world to perfect forms; the student held on to what was in front of him. He spent time on Lesbos catching sea creatures and cutting them open.
Why this question
Living things run to hundreds and thousands, all jumbled together. To know anything you must first sort them, and to sort them you need a criterion. By what do we call two things the same, and by what different? That question came first.
What was found
He divided first into creatures with blood and without. Then by whether they bear live young or lay eggs, where they live, how they move. In this way he recorded more than five hundred kinds. Grouping living things by chosen criteria is what we now call biological classification, and he built its first framework.
One judgment stands out. The dolphin lives in water, yet bears live young and suckles them. On that ground he pulled the dolphin out of the fishes — sorting by the structure of the body rather than by where it lives. It took two thousand years for that judgment to be granted again.
Living things were simply a multitude
Dissections and observations made on Lesbos
His way of sorting runs on to Linnaeus. But so did his notion that nature has a ladder with humans at the top