Final answer:
Democritus developed the philosophical idea of the atom in ancient Greece, proposing that all matter is made up of indivisible particles called atoms.
Step-by-step explanation:
The philosophical idea of the atom was developed by Democritus. Democritus was an ancient Greek philosopher who proposed that all matter is made up of small, indivisible particles called atoms. He believed that these atoms were constantly in motion and combined to form different substances. This idea laid the foundation for modern atomic theory.
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