Final answer:
Democritus could not test his atomic theory due to the limited technology of his era and the Greek philosophical emphasis on reason over experimentation.
Step-by-step explanation:
The reason why Democritus could not test his ideas about the atom primarily stems from limited technology during his time. The early Greek philosophers, including Democritus, heavily relied on reason and logic to understand the world, rather than on empirical experiment and observation. This philosophical approach was dominant, and they did not feel the necessity to experimentally validate their theories against life experiences or physical evidence. Consequently, despite Democritus proposing the concept of indivisible units of matter called 'atomos,' over two millennia passed before this theory of atoms was rediscovered and validated through scientific experimentation.