Eye of the king (Old Persian Spasaka?): inspector in the Achaemenid empire. Sometimes called "eyes and ears".
In his charming description of the youth of the founder of the Achaemenid empire, Cyrus the Great, the Greek researcher Herodotus of Halicarnassus suggests that the Median leader Astyages had several courtiers, one of them being the "eye of the king".note[Herodotus, Histories 1.114.] This is the first time this official, which is better known from the Achaemenid empire, is mentioned. It is not impossible that the Persians copied the office from the Medes.
The Persian Eyes were appointed by the king to inform him of what was going on in the empire. They supervised the payment of tribute, oversaw how rebellions were suppressed, and reported evils to the king. Inside their well-defined regions, they had more powers than the satraps. (According to the Athenian writer Xenophon, the Eyes also commanded armies to check satraps.note[Xenophon, Cyropaedia 8.6.16.]) Even when the monarch was not present, people knew that he would be informed of their actions and anxieties.
The Greeks knew the office. In his comedy Acharnians (first staged in 425), the Athenian playwright Aristophanes puts an Eye on the stage; the actor must have worn a mask that was painted with one big eye, so that he looked a bit like a cyclops. Almost a century later, Aristotle of Stagira was still impressed by the efficiency of the office:
The pomp of Cambyses and Xerxes and Darius was ordered on a grand scale and touched the heights of majesty and magnificence. The king himself, they say, lived in Susa or Ecbatana, invisible to all, in a marvelous palace [...]. Outside these the leaders and most eminent men were drawn up in order, some [...] called "guards" and the "listening-watch", so that the king himself [...] might see everything and hear everything.note[Aristotle, On the Cosmos 398a-b; tr. D.J. Furley.]
When the Athenians founded their empire in the early fifth century, they copied this institution, calling their inspectors episkopoi or "overseers". This title may have been a word-play, because this word sounds like the (probable) Persian name of the Eye: spasaka or "seer". However, this hypothetical.
The functions of the episkopos and the Eye were broadly similar: every town in the Athenian empire was supervised by an episkopos, who controlled the payment of the tributes, was supposed to prevent insurrections and had to investigate evils and report them to the Athenian government. Usually, the episkopos was chosen by the sovereign body in Athens, the people's assembly. The similarities are remarkable.
It should be stressed, however, that every ruler uses officials like the Eyes to know what is happening. The names of these inspectors may be different, but there are some primitive tasks that have to be executed anyway. For example, Charlemagne employed missi dominici. The Athenian government needed to send out inspectors, like all rulers had to do. Nevertheless, because the job responsibilities of the Eye and the episkopos are so very similar, we must seriously entertain the possibility that the Athenians copied a Persian function.
The title is not attested in the Seleucid and Parthian age; the reference by Philostratus,note[Philostratus, Life of Apollonius 28.] is almost certainly an anachronism.
J. Balcer, "The Athenian episkopos and the Achaemenid King's Eye" in: American Journal of Philology 98 (1977) 252-263.