Editing Diocletian (section)

==Reforms==

===Tetrarchic and ideological===
[[File:Head of Diocletian, Getty Museum.jpg|thumb|Head of Diocletian, [[Getty Museum]].<ref>{{Cite web |title=Fragment of a Togate Statue of Diocletian (The J. Paul Getty Museum Collection) |url=https://www.getty.edu/art/collection/object/103TG7 |access-date=2025-01-27 |website=The J. Paul Getty Museum Collection |language=en}}</ref>]]
Diocletian saw his work as that of a restorer, a figure of authority whose duty it was to return the empire to peace, to recreate stability and justice where barbarian hordes had destroyed it.{{sfn|Potter|2005|pp=294–295}} He arrogated, regimented and centralized political authority on a massive scale. In his policies, he enforced an Imperial system of values on diverse and often unreceptive provincial audiences.{{sfn|Potter|2005|p=298}} In the Imperial propaganda from the period, recent history was perverted and minimized in the service of the theme of the tetrarchs as "restorers". Aurelian's achievements were ignored, the revolt of Carausius was backdated to the reign of Gallienus, and it was implied that the tetrarchs engineered Aurelian's defeat of the [[Palmyrene Empire|Palmyrenes]]; the period between Gallienus and Diocletian was effectively erased. The history of the empire before the tetrarchy was portrayed as a time of civil war, savage despotism, and imperial collapse. In those inscriptions that bear their names, Diocletian, the "founder of eternal peace", and his companions are referred to as "restorers of the whole world", men who succeeded in "defeating the nations of the barbarians, and confirming the tranquility of their world". The theme of restoration was conjoined to an emphasis on the uniqueness and accomplishments of the tetrarchs themselves.{{sfn|Potter|2005|pp=294–298, quoting ''[[Inscriptiones Latinae Selectae|CIL]]'' 617, 618 & 641}}

The cities where emperors lived frequently in this period&nbsp;– [[Milan]], [[Trier]], [[Arles]], [[Sirmium]], [[Serdica]], [[Thessaloniki]], [[Nicomedia]] and [[Antioch]]&nbsp;– were treated as alternate imperial seats, to the exclusion of Rome and its senatorial elite.{{sfn|Corcoran|2006|pp=44–45}} A new style of ceremony was developed, emphasizing the distinction of the emperor from all other persons. The quasi-republican ideals of Augustus's ''[[primus inter pares]]'' were abandoned for all but the tetrarchs themselves. Diocletian took to wearing a gold crown and jewels, and forbade the use of [[Tyrian purple|purple cloth]] to all but the emperors.{{sfnm|1a1=Corcoran|1y=2006|1p=43|2a1=Potter|2y=2005|2p=290}} His subjects were required to prostrate themselves in his presence (''adoratio''); the most fortunate were allowed the privilege of kissing the hem of his robe (''[[proskynesis]]'', προσκύνησις).{{sfnm|1a1=CAH|1pp=171–172|2a1=Corcoran|2y=2006|2p=43|3a1=Liebeschuetz|3y=1979|3pp=235–252}} Circuses and basilicas were designed to keep the face of the emperor perpetually in view, and always in a seat of authority. The emperor became a figure of transcendent authority, a man beyond the grip of the masses.{{sfn|Potter|2005|p=290}} His every appearance was stage-managed.{{sfn|Southern|2001|pp=162–163}} This style of presentation was not new&nbsp;– many of its elements were first seen in the reigns of Aurelian and Severus&nbsp;– but it was only under the tetrarchs that it was refined into an explicit system.{{sfn|Southern|2001|pp=153–154, 163}}

===Administrative===
In keeping with his move from an ideology of republicanism to one of autocracy, Diocletian's council of advisers, his {{lang|la|consilium}}, differed from those of earlier emperors. He destroyed the Augustan illusion of imperial government as a cooperative affair among emperor, army, and senate.{{sfn|Southern|2001|pp=162–163}} In its place he established an effectively autocratic structure, a shift later epitomized in the institution's name: it would be called a {{lang|la|[[consistorium]]}}, not a council.{{sfnm|1a1=CAH|1pp=171–172|2a1=Southern|2y=2001|2pp=162–163|3a1=Williams|3y=1985|3p=110}}{{refn|The term {{lang|la|consistorium}} was already in use for the room where council meetings took place.{{sfn|CAH|p=172, citing the ''[[Codex Justinianus]]'' 9.47.12}}|group="Note"}} Diocletian regulated his court by distinguishing separate departments ({{lang|la|scrinia}}) for different tasks.{{sfnm|1a1=Southern|1y=2001|1pp=162–63|2a1=Williams|2y=1985|2p=110}} From this structure came the offices of different {{lang|la|magistri}}, like the {{lang|la|[[magister officiorum]]}} ("Master of Offices"), and associated secretariats. These were men suited to dealing with petitions, requests, correspondence, legal affairs, and foreign embassies. Within his court Diocletian maintained a permanent body of legal advisers, men with significant influence on his re-ordering of juridical affairs. There were also two finance ministers, dealing with the separate bodies of the public treasury and the private domains of the emperor, and the praetorian prefect, the most significant person of the whole. Diocletian's reduction of the Praetorian Guards to the level of a simple city garrison for Rome lessened the military powers of the prefect&nbsp;– although a prefect like Asclepiodotus was still a trained general&nbsp;– but the office retained much civil authority. The prefect kept a staff of hundreds and managed affairs in all segments of government: in taxation, administration, jurisprudence, and minor military commands, the praetorian prefect was often second only to the emperor himself.{{sfn|Williams|1985|pp=107–110}}

Altogether, Diocletian greatly increased the number of bureaucrats at the government's command; Lactantius claimed that there were now more men using tax money than there were paying it.{{sfn|Lactantius|loc=7}} The historian Warren Treadgold estimates that under Diocletian the number of men in the [[civil service]] doubled from 15,000 to 30,000.{{sfn|Treadgold|1997|p=19}} The classicist [[Roger S. Bagnall]] estimates that there was one bureaucrat for every 5–10,000 people in Egypt based on 400 or 800 bureaucrats for 4&nbsp;million inhabitants.<ref>{{cite book|first=Roger S. |last=Bagnall |year=1993 |title=Egypt in Late Antiquity |location=Princeton |publisher=Princeton University Press |isbn=0-691-06986-7 |page=66}}</ref>{{refn|No one knows the population of the province in 300&nbsp;AD; Strabo, 300 years earlier, put it at 7.5&nbsp;million, excluding Alexandria. By comparison, the ratio in 12th-century [[Song dynasty]] China was one bureaucrat for every 15,000 people.{{sfn|CAH|p=173|loc=fn. 6}}|group="Note"}} Jones estimated 30,000 bureaucrats, which he remarks is "not an extravagant number" given the size of the empire. He breaks down the bureaucracy as less than 12,000 provincial officials, and roughly 6,000 diocesan officials. For the military, he estimates a modest 300 officials per {{lang|la|[[magister militum]]}}, and 40 per {{lang|la|[[dux]]}}, for a total of about 5,000 military officials. For the [[praetorian prefect]] and [[Praefectus urbi|urban prefect]], he estimates approximately 5,000 clerks. He comments that the expense the empire paid for these was not high, as many lower-level clerks were not paid, and the wage of higher officials was generally modest.{{sfn|Jones|1964|p=1057}} 

To avoid the possibility of local usurpations,{{sfn|Carrié|Rousselle|1999|p=678}} to facilitate a more efficient collection of taxes and supplies, and to ease the enforcement of the law, Diocletian doubled the number of [[Roman province|provinces]] from fifty to almost one hundred.<ref>As taken from the ''{{lang|la|[[Laterculus Veronensis]]}}'' or ''Verona List'', reproduced in {{harvnb|Barnes|1982|loc=chs. 12–13}} (with corrections in {{cite journal |last=Barnes |first=Timothy D.|title=Emperors, panegyrics, prefects, provinces and palaces (284–317) |journal=Journal of Roman Archaeology |volume=9 |pages=532–552, at 548–550 |year=1996 |doi=10.1017/S1047759400017037|s2cid=250350035 }}). See also: {{harvnb|Barnes|1981|p=9}}; {{harvnb|CAH|p=179}}; {{harvnb|Rees|2004|pp=24–27}}.</ref> The provinces were grouped into twelve [[Roman diocese|dioceses]], each governed by an appointed official called a {{lang|la|[[vicarius]]}}, or "deputy of the praetorian prefects".{{sfnm|1a1=Barnes|1y=1981|1p=9|2a1=Rees|2y=2004|2pp=25–26}} Some of the provincial divisions required revision, and were modified either soon after 293 or early in the fourth century.{{sfn|Barnes|1981|p=10}} Rome herself (including her environs, as defined by a {{convert|100|mi|km|adj=on}}-[[radius]] [[perimeter]] around the city itself) was not under the authority of the praetorian prefect, as she was to be administered by a city prefect of senatorial rank&nbsp;– the sole prestigious post with actual power reserved exclusively for senators, except for some governors in Italy with the titles of corrector and the proconsuls of Asia and Africa.{{sfn|Carrié|Rousselle|1999|pp=655–666}} 

The dissemination of imperial law to the provinces was facilitated by Diocletian's reform of the Empire's provincial structure, which meant that there were now more governors ({{lang|la|[[Praeses|praesides]]}}) ruling over smaller regions and smaller populations.{{sfn|Potter|2005|p=296}} Diocletian's reforms shifted the governors' main function to that of the presiding official in the lower courts:{{sfnm|1a1=Harries|1y=1999|1pp=53–54|2a1=Potter|2y=2005|2p=296}} whereas in the early Empire military and judicial functions were the function of the governor, and [[Promagistrate|procurators]] had supervised taxation, under the new system {{lang|la|vicarii}} and governors were responsible for justice and taxation, and a new class of {{lang|la|[[Dux|duces]]}} ("[[duke]]s"), acting independently of the civil service, had military command.{{sfn|Williams|1985|p=107. There were still some governors&nbsp;– like Arpagius, the 298 governor of [[Britannia Secunda]]&nbsp;– who still busied themselves with military affairs in strained circumstances}} These dukes sometimes administered two or three of the new provinces created by Diocletian, and had forces ranging from two thousand to more than twenty thousand men.{{sfnm|1a1=Barnes|1y=1981|1pp=9–10|2a1=Treadgold|2y=1997|2pp=18–20}} In addition to their roles as judges and tax collectors, governors were expected to maintain the postal service ({{lang|la|[[cursus publicus]]}}) and ensure that town councils fulfilled their duties.<ref>{{harvnb|Rees|2004|p=25}} citing {{cite book|last=Corcoran| first=Simon |year=1996 |title=The Empire of the Tetrarchs: Imperial Pronouncements and Government A.D. 284–324 |location=Oxford |publisher=Clarendon Press |pages=234–253 |isbn=978-0-19-814984-2}}</ref>

This curtailment of governors' powers as the Emperors' representatives may have lessened the political dangers of an all-too-powerful class of Imperial delegates, but it also severely limited governors' ability to oppose local landed elites, especially those of senatorial status, which, although with reduced opportunities for office holding, retained wealth, social prestige, and personal connections,<ref>{{cite book|first=Michele Renee |last=Salzman |year=2009 |title=The Making of a Christian Aristocracy: Social and Religious Change in the Western Roman Empire |location=Cambridge, MA |publisher=Harvard University Press |isbn=978-0-674-00641-6 |page=31}}</ref> particularly in relatively peaceful regions without a great military presence.<ref>{{cite book|first=Inge |last=Mennen |year=2011 |title=Power and Status in the Roman Empire, AD 193–284 |location=Leiden |publisher=Brill |isbn=978-90-04-20359-4 |page=77}}</ref> On one occasion, Diocletian had to exhort a proconsul of Africa not to fear the consequences of treading on the toes of the local magnates of senatorial rank.{{sfn|Cod. Justinianus|loc=2.13.1}} If a governor of senatorial rank himself felt these pressures, the difficulties faced by a mere [[praeses]] were likely greater.{{sfn|Carrié|Rousselle|1999|p=678}} This led to a strained relationship between the central power and local elites: sometime during 303, attempted military sedition in [[Seleucia Pieria]] and [[Antioch]] prompted Diocletian to extract bloody retribution on both cities by putting to death a number of their council members for failing in their duties of keeping order in their jurisdiction.<ref>{{cite book|last=Leadbetter |first=Bill |year=2009 |title=Galerius and the Will of Diocletian |location=Oxford |publisher=Routledge |isbn=978-0-415-40488-4 |postscript=;}} {{cite book|last=Veyne |first=Paul |author-link=Paul Veyne |title=L'Empire Gréco-Romain |year=2005 |location=Paris |publisher=Seuil |isbn=2-02-057798-4 |at=p. 64 fn. 208}}</ref>

===Legal===
[[File:Digesto 02.jpg|thumb|upright|A 1581 reprint of the ''Digestorum'' from [[Justinian I|Justinian]]'s ''[[Corpus Juris Civilis]]'' (527–534). The ''Corpus'' drew on the codices of [[Codex Gregorianus|Gregorius]] and [[Codex Hermogenianus|Hermogenian]], drafted and published under Diocletian's reign.]]
As with most emperors, much of Diocletian's daily routine rotated around legal affairs&nbsp;– responding to appeals and petitions, and delivering decisions on disputed matters. Rescripts, authoritative interpretations issued by the emperor in response to demands from disputants in both public and private cases, were a common duty of second- and third-century emperors. In the "nomadic" imperial courts of the later Empire, one can track the progress of the imperial retinue through the locations from whence particular rescripts were issued&nbsp;– the presence of the Emperor was what allowed the system to function.<ref>{{cite book|first=Serena |last=Connolly |year=2010 |title=Lives behind the Laws: The World of the Codex Hermogenianus |location=Bloomington |publisher=Indiana University Press |isbn=978-0-253-35401-3 |page=61}}</ref> Whenever the imperial court would settle in one of the capitals, there was a glut in petitions, as in late 294 in Nicomedia, where Diocletian kept winter quarters.<ref>{{cite book|editor-last=Radner |editor-first=Karen |year=2014 |title=State Correspondence in the Ancient World: From New Kingdom Egypt to the Roman Empire |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-935477-1 |page=181}}</ref>

Admittedly, Diocletian's praetorian prefects&nbsp;– Afranius Hannibalianus, Julius Asclepiodotus, and [[Aurelius Hermogenianus]]&nbsp;– aided in regulating the flow and presentation of such paperwork, but the deep legalism of Roman culture kept the workload heavy.{{sfn|Williams|1985|pp=53–54, 142–143}} Emperors in the forty years preceding Diocletian's reign had not managed these duties so effectively, and their output in attested rescripts is low. Diocletian, by contrast, was prodigious in his affairs: there are around 1,200 rescripts in his name still surviving, and these probably represent only a small portion of the total issue.{{sfnm|1a1=CAH|1p=201|2a1=Williams|2y=1985|2p=143}} The sharp increase in the number of edicts and rescripts produced under Diocletian's rule has been read as evidence of an ongoing effort to realign the whole Empire on terms dictated by the imperial center.{{sfn|Potter|2005|pp=296, 652}}

Under the governance of the [[jurist]]s Gregorius, Aurelius Arcadius Charisius, and Hermogenianus, the imperial government began issuing official books of [[precedent]], collecting and listing all the rescripts that had been issued since the reign of [[Hadrian]] (r. 117–138).{{sfnm|1a1=Harries|1y=1999|1pp=14–15|2a1=Potter|2y=2005|2pp=295–296}} The [[Codex Gregorianus]] includes rescripts up to 292, which the [[Codex Hermogenianus]] updated with a comprehensive collection of rescripts issued by Diocletian in 293 and 294.{{sfn|Barnes|1981|p=10}} Although the very act of codification was a radical innovation, given the precedent-based design of the Roman legal system,{{sfn|Potter|2005|pp=295–296}} the jurists were generally conservative, and constantly looked to past Roman practice and theory for guidance.{{sfnm|1a1=Harries|1y=1999|1pp=21, 29–30|2a1=Potter|2y=2005|2pp=295–296}} They were probably given more free rein over their codes than the later compilers of the ''[[Codex Theodosianus]]'' (438) and ''[[Codex Justinianus]]'' (529) would have. Gregorius and Hermogenianus's codices lack the rigid structuring of later codes,{{sfn|Harries|1999|pp=21–22}} and were not published in the name of the emperor, but in the names of their compilers.{{sfn|Harries|1999|pp=63–64}} Their official character was clear in that both collections were acknowledged by courts as authoritative records of imperial legislation up to the date of their publication and regularly updated.<ref>{{cite book|first=George |last=Mousourakis |year=2012 |title=Fundamentals of Roman Private Law |location=Berlin |publisher=Springer |isbn=978-3-642-29310-8 |page=64}}</ref>

After Diocletian's reform of the provinces, governors were called ''iudex'', or [[judge]]. The governor became responsible for his decisions first to his immediate superiors, as well as to the more distant office of the emperor.{{sfn|Harries|1999|p=162}} It was most likely at this time that judicial records became verbatim accounts of what was said in trial, making it easier to determine bias or improper conduct on the part of the governor. With these records and the Empire's universal right of [[appeal]], Imperial authorities probably had a great deal of power to enforce behavior standards for their judges.{{sfn|Harries|1999|p=167}} In spite of Diocletian's attempts at reform, the provincial restructuring was far from clear, especially when citizens appealed the decisions of their governors. Proconsuls, for example, were often both judges of first instance and appeal, and the governors of some provinces took appellant cases from their neighbors. It soon became impossible to avoid taking some cases to the emperor for arbitration and judgment.{{sfn|Harries|1999|p=55}} Diocletian's reign marks the end of the classical period of Roman law. Where Diocletian's system of rescripts shows adherence to classical tradition, Constantine's law is full of Greek and eastern influences.{{sfn|CAH|p=207}}

Partly in response to economic pressures and in order to protect the vital functions of the state, Diocletian restricted social and professional mobility. Peasants became tied to the land in a way that presaged later systems of land tenure and workers such as bakers, armorers, public entertainers and workers in the mint had their occupations made hereditary.<ref>{{cite book|first=Richard |last=Lim |year=2010 |chapter=Late Antiquity |title=The Edinburgh Companion to Ancient Greece and Rome |publisher=Edinburgh University Press |location=Edinburgh |page=115}}</ref> Soldiers' children were also forcibly enrolled, something that followed spontaneous tendencies among the rank-and-file, but also expressed increasing difficulties in recruitment.{{sfn|Christol|Nony|2003|p=241}}

===Military===
{{See also|Late Roman army#Diocletian|l1=Late Roman army: Diocletian}}[[File:Bust of Diocletian at the National Museum of Serbia (cropped).jpg|thumb|Bust labelled as Diocletian at the [[National Museum of Serbia]]|218x218px]]It is archaeologically difficult to distinguish Diocletian's fortifications from those of his successors and predecessors. The [[Devil's Dykes]], for example—the Danubian earthworks traditionally attributed to Diocletian—cannot even be securely dated to a particular century. The most that can be said about built structures under Diocletian's reign is that he rebuilt and strengthened forts at the Upper Rhine frontier (where he followed the works built under [[Marcus Aurelius Probus|Probus]] along the [[Lake Constance]]-[[Basel]] and the Rhine–[[Iller]]–Danube line),{{sfn|Carrié|Rousselle|1999|p=166}} on the Danube (where a new line of forts on the far side of the river, the ''Ripa Sarmatica'', was added to older, rehabilitated fortresses),<ref name="Luttwak">{{cite book |last=Luttwak |first=Edward |year=1979 |title=The Grand Strategy of the Roman Empire |publisher=[[Johns Hopkins University Press]] |location=Baltimore |isbn=0-8018-2158-4 |page=176 }}</ref> in Egypt and on the frontier with Persia. Beyond that, much discussion is speculative and reliant on the broad generalizations of written sources. Diocletian and the tetrarchs had no consistent plan for frontier advancement, and records of raids and forts built across the frontier are likely to indicate only temporary claims. The ''[[Strata Diocletiana]]'', built after the Persian Wars, which ran from the Euphrates North of Palmyra and South towards northeast Arabia in the general vicinity of [[Bostra]], is the classic Diocletianic frontier system, consisting of an outer road followed by tightly spaced forts&nbsp;– defensible hard-points manned by small garrisons&nbsp;– followed by further fortifications in the rear.<ref name="Luttwak" />{{sfnm|1a1=CAH|1pp=124–126|2a1=Southern|2y=2001|2pp=154–155|3a1=Rees|3y=2004|3p=19–20|4a1=Williams|4y=1985|4pp=91–101}} In an attempt to resolve the difficulty and slowness of transmitting orders to the frontier, the new capitals of the tetrarchic era were all much closer to the empire's frontiers than Rome had been:{{sfnm|1a1=CAH|1p=171|2a1=Rees|2y=2004|2p=27}} Trier sat on the [[Moselle]], a [[tributary]] of the Rhine, Sirmium and Serdica were close to the Danube, Thessaloniki was on the route leading eastward, and Nicomedia and Antioch were important points in dealings with Persia.{{sfn|Rees|2004|p=27}}

Lactantius criticized Diocletian for an excessive increase in troop sizes, declaring that "each of the four princes strove to maintain a much more considerable military force than any sole emperor had done in times past. There began to be fewer men who paid taxes than there were who received wages; so that the means of the husbandmen being exhausted by enormous impositions, the farms were abandoned, cultivated grounds became woodland, and universal dismay prevailed".{{sfn|Lactantius|loc=7}} The fifth-century pagan [[Zosimus (historian)|Zosimus]], by contrast, praised Diocletian for keeping troops on the borders, rather than keeping them in the cities, as Constantine was held to have done.{{sfn|Corcoran|2006|p=46; quoting [[Zosimus (historian)|Zosimus]], [https://www.tertullian.org/fathers/zosimus02_book2.htm 2.34]}} Both these views had some truth to them, despite the biases of their authors: Diocletian and the tetrarchs did greatly expand the army, and the growth was mostly in frontier regions, where the increased effectiveness of the new Diocletianic legions seem to have been mostly spread across a network of strongholds.{{sfn|Christol|Nony|2003|p=241}} Nevertheless, it is difficult to establish the precise details of these shifts given the weakness of the sources.{{sfn|Southern|2001|p=157}}{{sfn|Treadgold|1997|p=19}} The army expanded to about 580,000 men from a 285 strength of 390,000, of which 310,000 men were stationed in the East, most of whom manned the Persian frontier. The navy increased from approximately 45,000 to approximately 65,000 men.{{sfn|Treadgold|1997|p=19}}{{refn|The 6th-century author [[John the Lydian]] provides extraordinarily precise troop numbers: 389,704 in the army and 45,562 in the navy.<ref>''[https://www.roger-pearse.com/weblog/wp-content/uploads/2017/12/John-Lydus-On-the-Months-tr.-Hooker-2nd-ed.-2017-1.pdf De Mensibus] {{Webarchive|url=https://web.archive.org/web/20230304225750/https://www.roger-pearse.com/weblog/wp-content/uploads/2017/12/John-Lydus-On-the-Months-tr.-Hooker-2nd-ed.-2017-1.pdf |date=4 March 2023 }}'' 1.27.</ref> His precision has polarized modern historians. Some believe that Lydus found these figures in official documents and that they are therefore broadly accurate; others believe that he fabricated them.{{sfn|Rees|2004|p=17}}|group="Note"}}

Diocletian's expansion of the army and civil service meant that the empire's tax burden grew. Since military upkeep took the largest portion of the imperial budget, any reforms here would be especially costly. The proportion of the adult male population, excluding slaves, serving in the army increased from roughly 1 in 25 to 1 in 15, an increase judged excessive by some modern commentators. Official troop allowances were kept to low levels, and the mass of troops often resorted to extortion or the taking of civilian jobs. Arrears became the norm for most troops. Many were even given payment in kind in place of their salaries. Were he unable to pay for his enlarged army, there would likely be civil conflict, potentially open revolt. Diocletian was led to devise a new system of taxation.{{sfnm|1a1=Southern|1y=2001|1pp=158–159|2a1=Treadgold|2y=1997|2pp=112–113}}

===Economic===

====Taxation====
{{main|Capitatio-Iugatio}}
In the early empire (30 BC&nbsp;– AD 235) the Roman government paid for what it needed in gold and silver. The coinage was stable. Requisition, forced purchase, was used to supply armies on the march. During the third-century crisis (235–285), the government resorted to requisition rather than payment in debased coinage, since it could never be sure of the value of money. Requisition was nothing more or less than seizure. Diocletian made requisition into tax. He introduced an extensive new tax system based on heads (''capita'') and land (''iugera'')&nbsp;– with one iugerum equal to approximately 0.65 acres&nbsp;– and tied to a new, regular census of the empire's population and wealth. Census officials traveled throughout the empire, assessed the value of labor and land for each landowner, and joined the landowners' totals together to make citywide totals of ''capita'' and ''iuga''.{{sfn|Treadgold|1997|p=20}} The ''iugum'' was not a consistent measure of land, but varied according to the type of land and crop, and the amount of labor necessary for sustenance. The ''caput'' was not consistent either: women, for instance, were often valued at half a ''caput'', and sometimes at other values.{{sfn|Southern|2001|p=159}} Cities provided animals, money, and manpower in proportion to its ''capita'', and grain in proportion to its ''iuga''.{{sfn|Treadgold|1997|p=20}}{{refn|The army recruitment tax was called the ''praebitio tironum'', and conscripted a part of each landowner's tenant farmers (''[[Colonus (person)|coloni]]''). When a ''capitulum'' extended across many farms, farmers provided the funds to compensate the neighbor who had supplied the recruit. Landowners of senatorial rank were able to commute the tax with a payment in gold (the ''aurum tironicum'').{{sfnm|1a1=CAH|1p=173|2a1=Rees|2y=2004|2p=18}}|group="Note"}}

Most taxes were due each year on 1 September, and levied from individual landowners by ''[[Decurion (administrative)|decuriones]]'' (decurions). These decurions, analogous to city councilors, were responsible for paying from their own pocket what they failed to collect.{{sfnm|1a1=Southern|1y=2001|1p=160|2a1=Treadgold|2y=1997|2p=20}} Diocletian's reforms also increased the number of financial officials in the provinces: more ''rationales'' and ''magistri privatae'' are attested under Diocletian's reign than before. These officials represented the interests of the fisc, which collected taxes in gold, and the Imperial properties.{{sfn|Barnes|1981|p=10}} Fluctuations in the value of the currency made collection of taxes in kind the norm, although these could be converted into coin. Rates shifted to take inflation into account.{{sfn|Treadgold|1997|p=20}} In 296, Diocletian issued an edict reforming census procedures. This edict introduced a general five-year census for the whole empire, replacing prior censuses that had operated at different speeds throughout the empire. The new censuses would keep up with changes in the values of ''capita'' and ''iuga''.{{sfn|Potter|2005|p=333}}

Italy, which had long been exempt from taxes, was included in the tax system from 290/291 as a diocesis.{{sfnm|1a1=Barnes|1y=1981|1pp=9, 288|2a1=Rees|2y=2004|2pp=28–29|3a1=Southern|3y=2001|3p=159}} The city of Rome remained exempt; the "regions" (i.e., provinces) South of Rome (generally called "suburbicarian", as opposed to the Northern, "annonaria" region) seem to have been relatively less taxed, in what probably was a sop offered to the great senatorial families and their landed properties.{{sfn|Carrié|Rousselle|1999|pp=187–188}}

Diocletian's edicts emphasized the common liability of all taxpayers. Public records of all taxes were made public.{{sfn|Williams|1985|p=125}} The position of ''decurion'', member of the city council, had been an honor sought by wealthy aristocrats and the middle classes who displayed their wealth by paying for city amenities and public works. Decurions were made liable for any shortfall in the amount of tax collected. Many tried to find ways to escape the obligation.{{sfnm|1a1=Southern|1y=2001|1p=160|2a1=Treadgold|2y=1997|2p=20}} By 300, civilians across the empire complained that there were more tax collectors than there were people to pay taxes.{{sfn|Brown|1989|p=25}}

====Currency and inflation====
[[File:Edict on Maximum Prices Diocletian piece in Berlin.jpg|thumb|A fragment of the [[Edict on Maximum Prices]] (301), on display in [[Berlin]]]]
[[File:Prices edict Greek.jpg|thumb|Part of the prices edict in Greek in its original area built into a medieval church, Geraki, Greece]]

Aurelian's attempt to reform the currency had failed; the denarius was dead.{{sfn|Southern|2001|p=160}} Diocletian restored the three-metal coinage and issued better quality pieces.{{sfn|Potter|2005|p=392}} The new system consisted of five coins: the ''aureus''/''[[solidus (coin)|solidus]]'', a gold coin weighing, like its predecessors, one-sixtieth of a pound; the ''[[argenteus]]'', a coin weighing one ninety-sixth of a pound and containing ninety-five percent pure silver; the ''[[follis]]'', sometimes referred to as the ''laureatus'' A, which is a copper coin with added silver struck at the rate of thirty-two to the pound; the ''radiatus'', a small copper coin struck at the rate of 108 to the pound, with no added silver; and a coin known today as the ''laureatus'' B, a smaller copper coin struck at the rate of 192 to the pound.{{sfn|Potter|2005|pp=392–393}}{{refn|The ''[[denarius]]'' was dropped from the Imperial mints,{{sfn|Southern|2001|p=160}} but the values of new coins continued to be measured in reference to it.{{sfn|Potter|2005|p=392}}|group="Note"}} Since the nominal values of these new issues were lower than their intrinsic worth as metals, the state was minting these coins at a loss. This practice could be sustained only by requisitioning precious metals from private citizens in exchange for state-minted coin (of a far lower value than the price of the precious metals requisitioned).{{sfn|CAH|pp=176–177}}

By 301, the system was in trouble, strained by a new bout of inflation. Diocletian, therefore, issued his ''Edict on Coinage'', an act re-tariffing all debts so that the ''[[nummus]]'', the most common coin in circulation, would be worth half as much.{{sfnm|1a1=Potter|1y=2005|1pp=334, 393|2a1=Southern|2y=2001|2p=160}} In the edict, preserved in an inscription from the city of [[Aphrodisias]] in [[Caria]] (near [[Geyre]], Turkey), it was declared that all debts contracted before 1 September 301 must be repaid at the old standards, while all debts contracted after that date would be repaid at the new standards.{{sfn|Potter|2005|pp=334–336}} It appears that the edict was made in an attempt to preserve the current price of gold and to keep the Empire's coinage on silver, Rome's traditional metal currency.{{sfn|Potter|2005|p=393}} This edict risked giving further momentum to inflationary trends, as had happened after Aurelian's currency reforms. The government's response was to issue a price freeze.{{sfn|CAH|pp=176–177}}

The [[Edict on Maximum Prices]] (''Edictum De Pretiis Rerum Venalium'') was issued two to three months after the coinage edict,{{sfn|Southern|2001|p=160}} somewhere between 20 November and 10 December 301.{{sfn|Potter|2005|pp=334–336}} The best-preserved Latin inscription surviving from the [[Greek East]],{{sfn|Potter|2005|pp=334–336}} the edict survives in many versions, on materials as varied as wood, papyrus, and stone.{{sfn|Southern|2001|p=160}}{{sfn|Southern|2001|p=339}} In the edict, Diocletian declared that the current pricing crisis resulted from the unchecked greed of merchants, and had resulted in turmoil for the mass of common citizens. The language of the edict calls on the people's memory of their benevolent leaders, and exhorts them to enforce the provisions of the edict, thereby restoring perfection to the world. The edict goes on to list in detail over one thousand goods and accompanying retail prices not to be exceeded. Penalties are laid out for various pricing transgressions.{{sfnm|1a1=CAH|1pp=177–178|2a1=Potter|2y=2005|2p=335|3a1=Southern|3y=2001|3p=161}}

In the most basic terms, the edict was ignorant of the law of [[supply and demand]]: it ignored the fact that prices might vary from region to region according to product availability, and it ignored the impact of transportation costs in the retail price of goods. In the judgment of the historian David Potter, the edict was "an act of economic lunacy".{{sfn|Potter|2005|p=335}} The fact that the edict began with a long rhetorical preamble betrays at the same time a moralizing stance as well as a weak grasp of economics&nbsp;– perhaps simply the wishful thinking that criminalizing a practice was enough to stop it. There is no consensus about how effectively the edict was enforced.{{sfn|Rees|2004|pp=42, 44}}

Supposedly, inflation, speculation, and monetary instability continued, and a [[black market]] arose to trade in goods forced out of official markets.{{sfn|CAH|pp=178}} The edict's penalties were applied unevenly across the empire (some scholars believe they were applied only in Diocletian's domains),{{sfn|CAH|pp=176–177}} widely resisted, and eventually dropped, perhaps within a year of the edict's issue.{{sfnm|1a1=Potter|1y=2005|1p=336|2a1=Southern|2y=2001|2p=161}} Lactantius has written of the perverse accompaniments to the edict; of goods withdrawn from the market, of brawls over minute variations in price, of the deaths that came when its provisions were enforced. His account may be true, but it seems to modern historians exaggerated and hyperbolic,{{sfnm|1a1=Lactantius|1loc=7.6–7|2a1=CAH|2p=178|3a1=Southern|3y=2001|3p=161}} and the impact of the law is recorded in no other ancient source.{{sfnm|1a1=Potter|1y=2005|1p=336|2a1=Williams|2y=1985|2pp=131–132}}