In 508, after a short period of old-fashioned aristocratic party struggles, the Athenian state was comprehensively reformed by Cleisthenes, whom Herodotus calls “the man who introduced the tribes and the democracy,” in that order. The order is important. Cleisthenes’ basic reform was to reorganize the entire citizen body into 10 new tribes, each of which was to contain elements drawn from the whole of Attica. These tribes, organized initially on nothing more than residence and not on the old four Ionian tribes based purely on descent, would from then on determine whether or not a man was Athenian and so fix his eligibility for military service.

The tribes were also the key part of the mechanism for choosing the members of a new political and administrative Council of Five Hundred, whose function it was to prepare business for the Assembly. The Council, or Boule, insofar as it was drawn roughly equally from each tribe, could be said to involve all Attica for the first time in the political process: all 140 villages, or demes, were given a quota of councillors—as many as 22 supplied by one superdeme and as few as 1 or 2 by some tiny ones. An interesting case has been made for saying that this political aspect was secondary and that the Cleisthenic changes were in essence and intention a military reform. Herodotus, for example, remarks on the military effectiveness of the infant Cleisthenic state, which had to deal immediately and successfully with Boeotian and Euboean invasions. And there were arguably attempts, within the Cleisthenic system, to align demes from different trittyes (tribal thirds) but the same tribe along the arterial roads leading to the city, perhaps with a view to easy tribal mobilization in the city centre. It is right that the political aspects of Cleisthenes (who was in fact far from producing democracy in the full sense) can too easily be overemphasized at the expense of the military; but the better view is that the new system had advantages on more than one level simultaneously.

One military result of Cleisthenes’ changes is not in dispute: from 501 on, military command was vested in 10 stratēgoi, or commanders (the usual translation “generals” obscures the important point that they were expected to command by sea as well as by land). Normally, each of the 10 tribes supplied one of these generals. They were always directly elected. Direct election for the stratēgia remained untouched by the tendency in subsequent decades to move in the general direction of appointment by lot. (Appointment by lot was more democratic than direct election because the outcome was less likely to be the result of manipulation, pressure, or a tendency to “deferential voting.”)

Even the Athenians were not prepared to sacrifice efficiency to democratic principle in this most crucial of areas. The number 10 remained sacrosanct and so (probably) did the “one tribe, one general” principle, though later in the 5th century, and in the 4th, it was possible for one tribe to supply two generals, one of whom was elected at the expense of the tribe whose candidate had polled the fewest votes. Again, the object was to ensure maximum efficiency: there might be two outstanding men in one tribe. Another peculiarity of the stratēgia, to be explained in the same way, was that reelection, or “iteration,” was possible. (Actually it is not quite certain that the stratēgia was unique in this respect; it is possible that iteration was possible for the archonship as well.)

The Cleisthenic system was based on the trittys, or tribal “third.” There were three kinds of trittys to each of the 10 tribes, the kinds being called “inland,” “coastal,” and “city.” There were therefore 30 trittyes in all, and each of the 139 demes belonged to a trittys and a tribe. The numbers of demes in a tribe could and did vary greatly, but the tribes were kept roughly equal in population as far as one can see. (The last words represent an important qualification: it is just possible that the whole system was overhauled in 403 to take account of changes in settlement patterns effected by the great Peloponnesian War. In that case the evidence for deme quotas—evidence which is mostly derived from 4th-century or Hellenistic inscriptions—would not be strictly usable for the 6th or 5th centuries. But in fact there is just enough evidence from the 5th century to make the assumption of continuity plausible.)

Each of the 10 tribes supplied 50 councillors to the new Council. In that way, even the remotest deme was involved in what happened in the city; Cleisthenes’ solution can thus be seen in its political aspect as an attempt to deal with a characteristic problem of ancient states, which were mostly agriculturally based. That problem was to avoid the domination of city assemblies by the urban population. Cleisthenes’ system gave an identity to the deme that it had not had before, even though the word dēmos just means “the people,” hence “where the people live,” hence “village” (the word and concept certainly predate Cleisthenes). Now it had a more precise sense: it was an entity with an identifiable body of demesmen and a right to representation in the Council.

The Cleisthenic deme was the primary unit for virtually all purposes. It was a social unit: to have been introduced to one’s demesmen in an appropriate context was good evidence that one was a citizen. It was the primary agricultural unit—though it is disputed whether all settlement in Attica was “nucleated” (that is, whether all farms were clustered together around demes), as one view holds. In fact, there is much evidence for nonnucleated (i.e., isolated) settlement. It was, as stated, a legal unit—although deme judges were suspended from 510 to the 450s. It was a financial unit: temple accounts from the distant deme of Rhamnus date from well back in the 5th century. It was a political unit: as shown, it supplied councillors to the new Council and enjoyed a vigorous deme life of its own (though it seems that there was little overlap between deme careers and city careers). It was a military unit: not only did tribes train together, but a dedication by the demesmen of Rhamnus may show that they participated as a group in the conquest of Lemnos by Miltiades the Younger about 500 bce. (Another view puts that inscription in the years 475–450 and sees it as a dedication by cleruchs or a garrison.) Above all it was a religious unit: deme religious calendars, some of the most informative of them published in the 1960s and ’70s, show a rich festival life integrated with that of the polis in a careful way so as to avoid overlap of dates. It has been suggested that the worship of Artemis of Brauron, a predominantly female affair, was somehow organized according to the 10-tribe system. Finally, and related to the last, it was a cultural unit: at the deme festival for Dionysus (the “Rural Dionysia”) there were dramatic festivals, subsidized, as inscriptions show, by wealthy demesmen and sometimes even by foreigners (one wealthy Theban is attested).

Cleisthenes seems also to have addressed himself to the definition of the Assembly, or Ecclesia. As seen, Solon admitted thētes to the Assembly, but Cleisthenes fixed the notional number of eligible Athenians (adult free male Athenians, that is) at 30,000. One-fifth of this total, 6,000, was a quorum for certain important purposes, such as grants of citizenship.

Cleisthenes’ ulterior motive in all this must remain obscure in the absence of any corpus of poetry by the man himself, of any biographical tradition, and even of good documentary or historiographic evidence from anywhere near Cleisthenes’ own time (the Constitution of Athens is reasonably full, but it was written nearly 200 years later).

That the tribal aspect of Cleisthenes’ changes was central was recognized even in antiquity, but Herodotus’s explanation, that he was imitating his maternal grandfather, Cleisthenes of Sicyon, does not suffice as an explanation on its own. The question is why he should have been anxious that each Athenian tribe should be a kind of microcosm of all Attica. Politically, the tribe does feature in Athenian public life (for instance, tribal support in lawsuits was valuable, and each of the 10 tribes presided by rotation over the Council for one-tenth of the year. This is the so-called prytany system). But the tribe was not a voting unit like the Roman tribe—Athenian votes were recorded as expressions of individual opinion, not submerged in some larger electoral or legislative bloc—and the later political functions of tribes were not quite numerous enough to explain why Cleisthenes felt it necessary to subdivide them into “thirds” in the way he did.

Cleisthenes’ changes should be seen in their context. First, the Attica he inherited had a relatively small number of militarily experienced fighters, many of them former Peisistratid mercenaries. It was essential that these be distributed among the tribes if the latter were to be militarily effective. (It is a corollary of this that one accepts that at some preliminary stage in Cleisthenes’ reforms there was widespread granting of citizenship to residents of Attica whose status was precarious. There was surely plenty of immigration into prosperous Peisistratid Attica, not all of it military in character.)

Second, in the late Archaic period tribal reform took place in other communities, some far removed from Attica in both character and geography. Cleisthenes’ system looks subtle, theoretical, and innovatory in its decimal approach to political reform and its reorganization of “civic space,” but there were precedents and parallels. For example, at Cyrene, three-quarters of a century after its colonization by Thera, there was stasis (political strife), which Demonax, a reformer who was called in from Mantinea on the mainland, settled by reorganizing Cyrene into three tribes. Again, at tyrannical or possibly posttyrannical Corinth, it seems (the evidence is some boundary markers published in 1968) that there was a tribal reorganization along trittys lines not dissimilar to, but earlier than, Cleisthenes’ system.

Finally, there is the Roman analogy: the new system of tribes and centuries, a system based partly on residence, replaced a purely gentilitial system—i.e., one based only on heredity. The word century is a clue: although the term signifies a voting unit, it is military in character. It is evident that tribal reform was a fairly general Archaic solution to the difficulties experienced by states with large numbers of immigrants. Such states needed the human resources these immigrants represented, but they could not admit them under the old rules. The rules had to be changed.

One may end with religion, which has been called a way of “constructing civic identity” in the ancient world, where religion was something embedded, not distinct. Cleisthenes was a decisive innovator in the social sphere, above all in the new role he allotted to the deme, but he did not dismantle the older social structures with their strong religious resonances. (The phratry, which was associated with Zeus and Apollo, continued to be an important regulator of citizenship; see above on the Demotionidai inscription.) His 10 new tribes were all named after heroes of Athenian or Salaminian myth, and those tribal heroes were objects of very active cult: this is in itself a recognition of a craving for a religiously defined identity. Nor did the old four Ionian tribes altogether disappear as religious entities; they are mentioned in a sacrificial context in a late 5th-century inscription and continued to matter in imperial contexts. (In the period of the 5th-century Athenian empire, some eastern Aegean islands and mainland cities went on using the names of the old four Ionian tribes for their civic subdivisions. That may help to explain the tribes’ importance in the Ion of Euripides, a play written in perhaps 413 bce, a time of imperial crisis.) The Cleisthenic Athenian state was still in many ways traditional, and it is above all in the religious sphere that one sees continuity even after Cleisthenes.