Democritus and Atomic Theory
Democritus came from Abdera in Thrace and reportedly traveled extensively through Egypt and Persia. Like other natural philosophers, he believed in the fundamental principle that nothing could come from nothing, and that true "change" was impossible. His genius was in finding a middle ground between Parmenides' strict Monism and Empedocles' pluralism.
His solution? Everything in the universe is made of tiny, eternal, and unchangeable particles called atoms (meaning "uncuttable"). These atoms differ from each other, explaining the variety in our world, yet each individual atom represents a perfect "One" in the Parmenidean sense. When objects appear to change, it's really just atoms rearranging themselves into new configurations.
Democritus was a strict materialist, believing only in physical matter and not in supernatural forces. This led him to a determinist worldview where everything operates according to mechanical necessity rather than purpose or design. He rejected teleology (the study of purpose in nature) in favor of seeking physical causes, asking "what caused this?" rather than "what purpose does this serve?"
Think About It: Bertrand Russell argued that philosophy's later preoccupation with purpose and design (rather than physical causes) actually hindered scientific progress until the Renaissance. Could Democritus have been ahead of his time?
Importantly, Democritus distinguished between qualities that exist in objects themselves (like weight and density) versus those that exist only in our perception (like taste and color). And since he believed the soul was just a collection of special atoms that disperse at death, he rejected the idea of immortality or eternal life.