Popper's political thought, particularly his idea of democracy, is usually thought akin to that of the liberal tradition. We don't challenge this position here, but claim the Popperian idea of democracy gains full meaning when some key ideas of Popper's own cosmology and epistemology are taken into account. Our contention is that Popper's political perspective is indeed rooted in his criticism to physical determinism and his studies on indeterminism. Notions such as "open universe" and "open society", when taken together, provide (...) a key to a liberal interpretation of cosmology and a physical interpretation of democracy. (shrink)