Cleisthenes was an Athenian political leader who introduced the concept of demokratia or "rule of the people" in 507 BC. This system of government replaced the existing system of aristocracy and gave more power to ordinary citizens. Under demokratia, all male citizens of Athens had the right to participate in the decision-making process through assemblies and juries. This marked a significant shift in power and paved the way for the development of democracy in the Western world. Today, democracy is the most prevalent system of government used globally.