Being ahead of one’s time was a bit ironic for Democritus, at least in the critical eyes of Aristotle. Here’s the story as retold by Frank N. Magill.* Some famous guy of ancient times died when an eagle dropped a turtle on his head. His contemporaries remembered that the oracle predicted he would be killed by Zeus’ lightning bolt. Okay, a turtle falling from the sky isn’t exactly a zigzag bolt of static electricity, but what are the chances of being hit by a falling turtle? Maybe Zeus forgot to recharge his lightning bolt battery that day, so he used a turtle. Democritus, as the story goes, knew about the guy’s death and the oracle’s prediction. Then one day as he was walking along the beach, he saw an eagle pick up a turtle and drop it on a rock to crack open its shell. Nifty trick, and birds using gravity to get at food is documented in our own times. Democritus recalled that the guy the turtle killed was bald. From above, he reasoned, his head might have appeared to be a rock.
And this is where Aristotle's criticism comes in: Aristotle faulted Democritus for seeing the past in the present when he looked at Nature.
Democritus began a way of thinking that can be found in modern science, particularly in geology. Sir James Hutton’s Principle of Uniformitarianism (term coined by William Whewell), though modified by modern geologists, stands as a modern version of Democritus’ thinking. Hutton realized that if, as an example, streams erode their banks today, they probably eroded their banks in the past. The processes of the present are probably not much different from the processes of the past. Applied to Democritus, the idea can be reduced to saying that what has happened can re-happen. Aristotle didn’t like that. He complained that Democritus pared down his explanations of Nature to the statement, “Thus it happened formerly, also.” If eagles pick up and drop turtles today, it’s a pattern they have had. The ancient bald guy just happened to be in the wrong place at the wrong time and just happened to look from the perspective of an eagle like a rock. Democritus made a reasonable assumption based on an observation.
“Thus it happened formerly also” might not have been Aristotle’s way of thinking. In his criticism of Democritus, however, he missed what Democritus and the eighteenth-century “Father of Geology” Hutton had not missed. There’s a consistency to the world that we rely on if we want to achieve a scientific explanation. Anomalies are tough to deal with. So, we look for some consistency when we construct theories from hypotheses. And we do so when we deal with one another. In explaining behavior and thought in others, we are very much students in the school of Democritus and Hutton. We believe “thus it happened formerly also.” If a person was "a certain way" before, well, that’s the way the person has to be now.
Recognizing that people can effect change in their lives is difficult for all of us. Oh! Not in general, but specifically. That is, those whom we have known and who have “dropped turtles on rocks” still, in our way of thinking “drop turtles on rocks.” It’s in their nature, we think. If we see the past recaptured in the present in our physical surroundings, why shouldn’t we think we see the past recaptured in the present behavior and thought of those with whom we associate or with strangers we want to “explain”? We are behavioral uniformitarians, particularly in regard to "bad" behavior. For us, the past often presages the present.
“Formerly, also” works in physical Nature. “Formerly, also” is not necessarily applicable to human nature.
*Magill, Frank N., Ed. Masterpieces of World Philosophy, HarperCollins Publishers, 1990, p 19.