it is thanks chiefly to Plato that the scientists and philosophers known collectively as the Presocratics, of whom Democritus was the last, have almost without exception not survived to address us in their own right. For it was a major part of Plato's purpose, showing himself in this respect at any rate fully representative of the agonistic or competitive character of all ancient Greek intellection, to put out of court and drive from the market all earlier philosophers apart from Socrates — or at any rate his representation of 'Socrates'. This aim he achieved with near-total success.That is very interesting. Some people assume we don't have more older books because they decayed. But which ones were preserved is not random and calls out for explanation.
This is quoting Democritus on page 24:
Nature and teaching are closely related; for teaching reforms a person, and by reforming remakes his nature.The idea that nature can be changed is one of the major things missing from the current nature/nurture debate that assumes traits due to nature are permanent but traits due to nurture can be changed.
One more quote of Democritus from page 32:
Even when you are alone, neither say nor do anything bad: learn to feel shame before yourself rather than before others.Here he anticipates Feynman's advice not to orient your life around what other people think, and connects it to morality.