ensuing civil war. Though able rulers, such as Trajan ( AD 98
to 117), Hadrian, and Marcus Aurelius in the next century,
could stanch decline, they could not, or did not want to,
address the fundamental institutional problems. None of
these men proposed abandoning the empire or re-creating
effective political institutions along the lines of the Roman
Republic. Marcus Aurelius, for all his successes, was
followed by his son Commodus, who was more like
Caligula or Nero than his father.
The rising instability was evident from the layout and
location of towns and cities in the empire. By the third
century AD every sizeable city in the empire had a defensive
wall. In many cases monuments were plundered for stone,
which was used in fortifications. In Gaul before the Romans
had arrived in 125 BC , it was usual to build settlements on
hilltops, since these were more easily defended. With the
initial arrival of Rome, settlements moved down to the
plains. In the third century, this trend was reversed.
Along with mounting political instability came changes in
society that moved economic institutions toward greater
extraction. Though citizenship was expanded to the extent
that by AD 212 nearly all the inhabitants of the empire were
citizens, this change went along with changes in status
between citizens. Any sense that there might have been of
equality before the law deteriorated. For example, by the
reign of Hadrian ( AD 117 to 138), there were clear
differences in the types of laws applied to different
categories of Roman citizen. Just as important, the role of
citizens was completely different from how it had been in
the days of the Roman Republic, when they were able to
exercise some power over political and economic
decisions through the assemblies in Rome.
Slavery remained a constant throughout Rome, though
there is some controversy over whether the fraction of
slaves in the population actually declined over the
centuries. Equally important, as the empire developed,
more and more agricultural workers were reduced to semi-
servile status and tied to the land. The status of these
servile “coloni” is extensively discussed in legal documents
such as the Codex Theodosianus and Codex Justinianus ,
and probably originated during the reign of Diocletian ( AD
284 to 305). The rights of landlords over the coloni were