The extensive use of Betrand Russels great but very personal history of philosophy as a source is probably to blame. The article should have a section with criticism of Democritus, and the whole idealist vs. materialist discussion could be outlined here. An encyclopaedia article do not need an conclusion. Instead of a lot of assumptions of the superiority of mechanistic thinking, there could be a section with influences (all materialists - Hobbes, Marx... John Dalton for the atom - and maybe (it seems)  Russel)