Athenian democracy : 'Old Oligarch' and the oligarchy of 400

One of the earliest criticisms against Athenian democracy that having been heavily modified by Pericles, came from ‘an Athenian writer whom we know familiarly as the “Old Oligarch”… His short and vehement pamphlet was produced probably in the 420s, during the first decade of the Peloponnesian War, and makes the following case: democracy is appalling, since it represents the rule of the poor, ignorant, fickle and stupid majority over the socially and intellectually superior minority, the world turned upside down’ (http://www.bbc.co.uk/history/ancient/greeks/greekcritics_01.shtml). However, such criticism from ‘an oligarch’, who might have represented the traditional ruling class now facing the problem of losing its dominance in politics, did not seem to be heard because ‘at the time of writing, Athens was the greatest single power in the entire Greek world’ (ibid) and ‘the ultimate source of Athens’ power was its navy’ (ibid), which relied on the arms of the thetes, in effect ‘the poorest section of the Athenian citizen population(ibid).
Nevertheless, as the war continued, Athenian politics changed its course in the following way:

‘In 415, after an interlude of relative peace in the war between Athens and Sparta, the Demos of Athens undertook an invasion of Sicily. This adventure was an utter disaster, resulting in the destruction of an Athenian fleet and an army of Athenian citizens… In the aftermath, certain citizens took steps to move the government of the city away from the radical democracy that—they thought—was leading the city to ruin… Shortly thereafter, in 411 BCE, the Athenians brought an end to their democracy and instituted an oligarchy by, first, appointing ten “Commissioners”… These Commissioners proposed a new Council, consisting of 400 men, with service limited to the wealthier citizens… This oligarchic government lasted only four months before it was replaced by another government in which the power was in the hands of 5000 Athenians’ (http://www.stoa.org/projects/demos/article_democracy_development?page=6).

Invasion of Sicily

For reading the text in full:  http://wrex2009.wordpress.com/2014/09/12/platos-republic-with-its-historical-background/