The Athenian democracy of Cleisthenes and Pericles was based on freedom of citizens (through the reforms of Solon) and on equality of citizens (isonomia) - introduced by Cleisthenes and later expanded by Ephialtes and Pericles. To preserve these principles, the Athenians used lot for selecting officials. Casting lots aimed to ensure that all citizens were ""equally"" qualified for office, and to avoid any corruption allotment machines were used. Moreover, in most positions chosen by lot, Athenian citizens could not be selected more than once; this rotation in office meant that no-one could build up a power base through staying in a particular position.