Among other things,optimates have been seen as supporters of the continued authority of thesenate, politicians who operated mostly in the senate, or opponents of thepopulares.[6] Thepopulares have also been seen as focusing on operating before thepopular assemblies, generally in opposition to thesenate,[7] using "the populace, rather than the senate, as a means [for advantage]".[8] References tooptimates (also calledboni, "good men") andpopulares are found among the writings of Roman authors of the 1st century BC. The distinction between the terms is most clearly established inCicero'sPro Sestio, a speech given and published in 56 BC,[9][10] where he framed the two labels against each other.
With the publication of theRömische Geschichte in the 1850s, the German historianTheodor Mommsen set the enduring and popular interpretation thatoptimates andpopulares represented political parties, which he implicitly compared to the German liberal and conservative parties of his own day. Mommsen's paradigm, however, has been criticised by generations of historians, first byFriedrich Münzer, followed byRonald Syme, who considered that Roman politics was marked by familial and individual ambitions, not parties. Other historians have pointed to the impossibility of applying such labels to many individuals, who could pretend to bepopularis oroptimas as they saw fit; the careers ofDrusus orPompey are for example impossible to fit into one "party". Ancient usage was also far from clear: even Cicero, while linkingoptimates to Greekaristokratia (ἀριστοκρατία), also used the wordpopulares to describe politics "completely compatible with... honourable aristocratic behaviour".[11]
As a result, modern historians do not recognise any "coherent political party" under eitherpopulares oroptimates,[12] nor do those labels lend themselves easily to comparison with a modern left–right split.[13] Democratic interpretations of Roman politics, however, have pushed for a re-evaluation which attributes an ideological tendency – e.g.populares believing inpopular sovereignty – to the labels.[14]
With the publication of theRömische Geschichte in the 1850s, the German historianTheodor Mommsen set the enduring and popular interpretation thatoptimates andpopulares represented aristocratic and democratic parliamentary-style political parties, with the labels emerging around the time of the Gracchi.[15] His interpretation "owe[d] much to nineteenth century German liberal thought".[16] Classicists today, however, generally agree that neitheroptimate orpopularis referred to political parties: "It is common knowledge nowadays thatpopulares did not constitute a coherent political group or 'party' (even less so than their counterparts,optimates)".[12]
Unlike in modern times, Roman politicians stood for office on the basis of their personal reputations and qualities rather than with a party manifesto or platform.[17] For example, the opposition to theFirst Triumvirate failed to act as a united front with coherent coordination of its members,[18] acting instead on an ad hoc basis with regular defections to and from those opposing the political alliance depending on the topic of debate, personal relations, etc. These ad hoc alliances and many different methods of gaining political influence meant there were no "neat categories ofoptimates andpopulares" or of conservatives and radicals in a modern sense.[13] Erich S Gruen, for example, inLast Generation of the Roman Republic (1974) rejected bothpopulares andoptimates, saying "such labels obscure rather than enlighten" and arguing thatoptimates was used not as a political label, but instead used to praise a member of the political elite.[19]
Moving away from the 19th century view of political parties or factions vying for dominance, the scope of the modern academic debate focuses on whether the terms referred to an ideological split among aristocrats or whether the terms were meaningless or topics of debate themselves.[20]
The traditional view of theoptimates refers to aristocrats who defended their own material and political interests and behaved akin to modern fiscal conservatives in opposing wealth redistribution and supporting small government.[21][a] To that end, theoptimates were viewed traditionally as emphasising the authority or influence of the senate over other organs of the states, including the popular assemblies.[21] In other instances, theoptimates are defined "somewhat mechanically, as those who opposed thepopulares".[21]
This definition relying on a "senatorial" party or fiscal conservatives breaks down at a closer reading of the evidence.[23] A "senatorial" party describes no meaningful split, as basically all active politicians were senators.[b]
A definition to the terms based on whether a politician supported land redistribution or grain subsidies runs into two issues. Such measures were not "the sole preserve of the so-called populares" and "were not per se incompatible with traditional senatorial policy, given the extensive colonisation the senate had overseen in the past and the grain provision which members of the elite occasionally organised on a private basis".[25] Moreover, identifying thepopulares based on the policies they supported in office would place politicians traditionally identified as belonging to one "faction" into the "opposite" camp:[26]
Publius Sulpicius Rufus, one of the classicpopulares, supported policies that had little "to do with the betterment of thepopulus and in fact appear to have been distinctly unpopular".[27]
Marcus Livius Drusus, brought agrarian reform laws with the support of the senate, giving his policies apopularis tone,[25] even when senatorial support and agrarian reforms are supposedly dichotomous.
Cato the Younger, traditionally identified astheoptimate, becomespopularis for supporting expansion of the grain dole during histribunate.[25]
Sulla, traditionally identified also as an arch-conservative, turnspopularis for "probably confiscat[ing] and redistribut[ing] more land in Italy than any other Roman politician".[26]
AndJulius Caesar, traditionally seen aspopularis (though never self-identifying with that label in his extant texts[3]), emerges as anoptimate for "substantially reduc[ing] the number of grain recipients in Rome during his dictatorship".[28]
Other proposed views ofoptimates are that they were leaders of the senate[29] or those acting with the support of the senate.[30] Mouritsen inPolitics in the Roman Republic (2017) rejects both of the traditional definitions. Ofoptimates being those with the support of the senate:
the category becomes devoid of any political content, since the majority would always be "optimates" whatever policy they happened to agree on. In other words, if we follow Meier's approach to its logical conclusion, the two concepts become virtually meaningless, as illustrated by the famous vote in December 50 when the senate rejected the hard-line "optimate" opponents of Caesar and endorsed Curio's compromise option by 370 to 22. On that occasion the leading "optimates" did not have the rest of the senate behind them, effectively turning men like Cato into "populares".[31]
Usage of the term by contemporaries also was not highly dichotomised.Optimate was used generically to refer to the wealthy classes in Rome as well as the aristocracies of foreign cities or states:[32]
As a standard term for the ruling class [optimates] was widely used, often in parallel withboni, which denoted the propertied classes in general and therefore overlapped withoptimates. Its generic nature is illustrated by the fact that it could be employed about foreign aristocracies... If we accept this definition ofoptimates as a term denoting the senatorial elite, the so-calledpopulares – qua senators – themselves becomeoptimates, precluding any meaningful distinction.[29]
Denarius of Gaius Minucius Augurinus, 135 BC, depicting a grain distribution.[33] Grain distribution is traditionally held to be one of the recurrent topics ofpopularis agitation.
References topopulares in scholarship today "do not imply a co-ordinated 'party' with a distinctive ideological character, a kind of political grouping for which there is no evidence in Rome, but simply allude to a... type of senator" who is "at least at that moment acting as the people's man".[34] This is in contrast to the 19th century view of thepopulares from Mommsen, in which they are a group of aristocrats which supported democracy and the rights and material interests of the common people.[15]
The highly influential view of Christian Meier redefined thepopularis as a label for a senator using the popular assemblies' law-making powers to overrule decisions of the senate, primarily as a political tactic to get ahead in Roman politics.[35] In this view, apopulares politician is a person who:
[adopts] a certain method of political working, to use the populace, rather than the senate, as a means to an end; the end being, most likely, personal advantage for the politician concerned.[8]
Theratio popularis, or strategy of putting political questions before the people writ large, was pursued when politicians were unable to achieve their goals through the normal process in the senate.[36][37] This was in part structural: the "dyadic nature of [the senate and people of Rome, ie the republic] meant that when a senator opposed his peers... there was only recourse available" to the people.[38] This political method involved a populist style of rhetoric, and "only to a limited extent, that of policy" with even less ideological content.[39][40]
The content ofpopularis legislation was tied to the fact that politicians choosing to go before the people required needed strong support therefrom to overrule the decision of the senate. This forced politicians choosing a popular strategy to include policies that directly benefited voters in the assemblies, such as debt relief, land redistribution,[41][pages needed] and grain doles. The earlierpopularis tactics ofTiberius Gracchus reflected the dominance of rural voters who had resettled to Rome recently, while the laterpopularis tactics ofClodius reflected the interests of the masses of urban poor.[37]
Material interests like corn subsidy bills were not the whole ofpopularis causes:[42]popularis politicians also may have made arguments on the proper role of the Assemblies in the Roman state (ie, a popular sovereignty) rather than just questions of material interests.[43] Other benefits proposed attempted to empower supporters in the popular assemblies, with introduction of secret ballot, restoration of tribunician rights afterSulla's dictatorship, promotion of non-senators onto juries before the law courts, and the general election of priests. All of these empowered non-senatorial supporters broadly, including both the wealthyequites and the poor urban population in Rome.[44]
One of the larger issues in modern scholarship is whether the politicians who operated in theratio popularis actually believed in their proposals, scepticism of which "certainly seems well warranted in many cases".[45]
A democratic interpretation of Roman politics neatly complements an ideological revival by interpreting Roman politicians to vie for popular support at an ideological, but not factional, level.[46] This link, however, remains tenuous, as "candidates apparently never ran on specific policies or associated themselves with particular ideologies during their campaign[s]".[46] Moreover, speculation as to the inner motivations of Roman politicians cannot be substantiated one way or the other, as the inner thoughts of the Roman elite are almost entirely lost.[47] Even the apparent deaths suffered by "popularis" tribunes cannot be accepted at face value: initial intentions are not final outcomes, it is unlikely that those who followed apopularis path expected death.[48]
Mackie argued thatpopularis politicians had an ideological bent towards criticising the senate's legitimacy, focusing on the sovereign powers of the popular assemblies, criticising the senate for neglecting common interests, and accusing the senate of administering the state corruptly.[49] She added thatpopulares advocated for the popular assemblies to take control of the republic, phrasing demands in terms oflibertas, referring to popular sovereignty and the power of the Roman assemblies to create law.[50] T. P. Wiseman argues, further, that these differences reflected "rival ideologies" with "mutually incompatible [views on] what the republic was".[51]
This democratic interpretation did not imply a party structure, instead focusing on motivations and policies.[52] Scholars of the late republic have not reached a consensus as to whether Roman politicians really were divided in these terms.[52] Nor does an ideological approach explain the traditional identification of certain politicians (egPublius Sulpicius Rufus) aspopularis when the policies they advanced were only weakly connected to the welfare of the Roman voter.[30] Robb argues, moreover, that the premise of the label, ie that a certain person or policy benefits the people write large, is of little use: "the principle of acting in the popular interest was a central one that all politicians would claim to be following".[53]
The "constitutional framework in which politicians operated automatically turned policy disagreements into rhetorical contests betweenpopulus and aristocracy": tribunes which were unable to secure the support of their peers in the senate would naturally go before the people; to justify this they turned to stock arguments for popular sovereignty; opponents would then bring out similar stock arguments for senatorial authority.[54] Young Roman politicians also turned regularly to controversial rhetoric or policies in an attempt to build their name recognition and stand out from the mass of other political candidates in their short one-year terms, with few apparent negative impacts on their longer-term career prospects.[55]
Popularis rhetoric was couched "in terms of the consensus of values at Rome at the time:libertas,leges,mos maiorum, and senatorial incompetence at governing theres publica".[56] In public speeches during the republic, legislative disagreements did not emerge in party-political terms: "from the rostra... neither the opponents ofTiberius Gracchus, nor Catulus against Gabinius, nor Bibulus against Caesar, nor Cato against Trebonius even so much as suggested that their advice to thepopulus was predicated on an 'optimate' policy based on a different arrangement of political ends and means from those of the 'popular' advocates of a bill... there was, it seems, virtually no place on the rostra for ideological bifurcation".[57] For the Roman in the street, political debate was not related to party affiliations, but the issue and proposer itself: "Is the proposer of this agrarian (or frumentary, etc.) law really championing our interests, as he avows, or is he rather pursuing some private benefit for himself or something else behind the scenes?" which naturally flowed into the themes of personal credibility that recur in republican public rhetoric.[58]
Like most Roman rhetoric,popularis rhetoric also drew heavily on historical precedents (exempla) – including that from ancient times, such as the revival of thecomitia Centuriata as a popular law court,[59] – from the abolition of the Roman monarchy to the popular rights and liberties won by the secession of the plebs.[60]Popularis rhetoric surrounding secret ballots and land reform were not framed in terms of innovations, but rather, in terms of preserving and restoring the birth-right liberty of the citizenry.[61] Andpopulares too could hijack traditionallyoptimate themes by criticisingcurrent senators for failing to live up to the examples of their ancestors, acting in ways which would in the long run harm the authority of the senate, or framing their own arguments in fiscal responsibility.[62][63]
Both putative groups agreed on core values such as Roman liberty and the fundamental sovereignty of the Roman people; even those who were supporting the senate at some time or another would not be able to wholly discount the traditional sovereignty attributed to the people.[45][64] Furthermore, much of the perceived difference betweenoptimates andpopulares emerged from rhetorical flourishes unsupported by policy: "no matter how emphatically the people’s interests and 'sovereignty' may have been asserted, the republic never saw any concrete attempts to change the nature of Roman society or shift the balance of power".[54]
Beyond the modern usage of the two terms in classical studies to refer to the putative political parties, the terms also emerge from the Latin literature of the period.
InLatin, the wordpopularis is normally used outside the works of Cicero to mean "compatriot" or "fellow citizen".[65] The word also could be used pejoratively to refer to populists or politicians pandering to the people, politicians with great personal popularity, politicians who were ostensibly acting in the peoples' interest, and actions before crowds of the people.[46]
The wordoptimates, while infrequent in the surviving canon, is also used to refer to aristocrats or the aristocracy as a whole.[66]
In Cicero's letters – rather than his forensic speeches – he used it generally to refer to popularity.[65] In Cicero's philosophical works, it was used to refer to "the majority of the people" and to describe "the style of speech most useful for public speaking".[67]
The oppositional meaning betweenpopulares andoptimates emerges mainly fromCicero's drawing of a distinction between the two in his speechPro Sestio, a speech made to defend a friend instrumental in recalling Cicero from exile by his political enemyClodius.[68] Cicero's use of the term, that "populares aim to please the multitude", is recognised to be polemical.[12] His remarks thatpopularis tactics emerged from a failure to win the support of the senate and of personal grievances with the senate are also "equally suspect".[8] Cicero's usage in that speech draws a distinction betweenoptimates who "are honourable, honest, and upright... [and] safeguard the interests of the state and the liberty of its citizens" withpopulares who are not so honourable and instead engage in failed attempts to cultivate demagoguery.[69] Cicero's description of Clodius aspopularis "concentrates on the demagogic sense of the word, rather than risking attack on the rights of the people".[70]
Mouritsen writes of Cicero inPro Sestio:
Cicero’s bold rhetorical self-reinvention in thePro Sestio has presented historians with a deceptively simple model which at first sight seems to provide a key to unlocking the secrets of Roman politics. But the terminology Cicero uses turns out to be unique and unlike anything else found in the ancient sources... We are therefore not dealing with an observable phenomenon for which thePro Sestio happens to offer a convenient label. Rather, it is the other way round: Cicero’s use ofpopularis in that particular speech has reified what would otherwise have remained discrete difficult-to-classify events and individuals and turned them into manifestations of a single political movement.[71]
Cicero, however, did not always use the word this way. During his consulship, he "stak[ed] his own claim to beingpopularis [in] the popular mandate he [held] as an elected consul" and drew a distinction between himself and other politicians as to who truly acted in the interests of the Roman people.[72] This usage did not draw a contrast betweenpopulares andoptimates.[73] He similarly uses the termpopularis describe himself in theSeventh Phillipic for his opposition to Antony and later, in the Eighth Phillipic, to describe the actions ofNasica andOpimius "for having acted in the public interests" by killingTiberius Gracchus andGaius Gracchus.[74] This usage also does not contrast tooptimates but instead suggests that some person is "truly acting in the interest of the people".[75]
Sallust, a Roman politician who served as praetor during Caesar's dictatorship, writing an account of theCatiline conspiracy and theJugurthine war, does not use the wordoptimas (oroptimates) at all, and uses the wordpopularis only ten times. None of those usages are political, referring either to countrymen or comrades.[76] Robb speculates that "[Sallust] may have chosen the avoid using the word precisely because it was so imprecise and did not clearly identify a particular kind of politician".[77]
In his work on theJugurthine war, he does have a narrative of two parties: one of the people (populus) and one thenobles (nobilitas), where a small and corrupt section of the senate (pauci, 'the few') is contrasted oligarchically against the rest of society. But because thenobiles were defined not by their ideology, but by their ancestry from past holders of curule magistracies, these are not theoptimates of ideological or political-party conflict, who are themselves "riven by internal divisions".[78]
Sallust also fails to draw any distinction between popular sovereignty and senatorial prestige as sources of legitimacy or authority.[79] He also gives the "dissenting nobles and their factions" no labels, "for the simple reason that they lacked the common characteristics which would have enabled such a categorisation",[80] instead presenting a cynical view in which Roman politicians cloaked themselves opportunistically in terms oflibertas populi Romani andsenatus auctoritas as means for self-advancement.[81]
While ancient accounts of the late republic describe "a political 'establishment' and the opposition" thereto they do not use words such aspopulares to describe that opposition.[82] Because politicians viewed their own status as reflected by the support of the people, the latter acting passively as a judge of "aristocratic merit", all politicians claimed "to be 'acting in the interest of the people', or in other words,popularis".[82] Words used to describe dissent in the vein ofGaius Gracchus andQuintus Varius Severus trended more towardsseditio andseditiosus.[38]
The works ofLivy, the author ofAb Urbe Condita Libri (known in English as theHistory of Rome), have been used to argue in favour of a distinction betweenpopulares andoptimates through to earlier periods such as theConflict of the Orders. Livy wrote after the late republic, during the Augustan period.[83] However, his treatment of the late Republic does not survive except in an epitome called thePeriochae. While it is generally accepted that "Livy applies late republican political language to events from earlier periods", the termsoptimates andpopulares (and derivatives) appear infrequently and generally not in a political context.[66]
The vast majority of the usages ofpopularis in Livy denote fellow citizens, comrades, and oratory suitable for public speaking.[84] Usage ofoptimates is also infrequent, the majority of usages referring to foreign aristocrats.[66] Livy's terminology in describing the conflict of the orders referred not topopulares andoptimates but rather toplebeians andpatricians and their place in the constitutional order.[85] Livy only uses the wordpopularis in contrast tooptimates in political terms only once, in a speech put into the mouth of Barbatus on the tyranny of theSecond Decemvirate in the 450s BC, centuries before the late republic.[86]
By the 1930s, a far less ideological interpretation emerged, viewing Roman republican politics as dominated by parties, not of like-minded ideologues, but of aristocraticgentes.[91] Syme in the 1939 bookRoman Revolution wrote that:
The political life of the Roman Republic was stamped and swayed, not by parties and programmes of a modern and parliamentary character, not by the ostensible opposition between senate and people,optimates andpopulares,nobiles andnovi homines, but by the strife for power, wealth and glory. The contestants were thenobiles among themselves, as individuals or in groups, open in the elections and in the courts of law, or masked by secret intrigue.[92]
Syme's description of Roman politics viewed the late republic "as a conflict between a dominant oligarchy drawn from a set of powerful families and their opponents" which operated primarily not in ideological terms, but in terms of feuds between family-based factions.[93] Strausberger, writing also in 1939, challenged the traditional view of political parties, arguing that "there was no 'class war'" in the various civil wars (egSulla's civil war andCaesar's civil war) that started the collapse of the republic.[94]
Meier noted in 1965 that "'popular' politics was very difficult both to understand and describe[, noting] that the people itself had no political initiative but was 'directed' by the aristocratic magistrates it elected[, meaning that] 'popular' politics was... the province of politicians not the people".[95] Moreover, "very few 'populares' appeared to embrace long term goals and most acted in a way described aspopularis for only a short time".[95]
He suggested four meanings for the wordpopularis:
politicians acting as champions of the people against the senate,
politicians manipulating the popular assemblies,
politicians who took up acausa populi and paraded the people before theplebs urbana, and
a manner adopted by politicians who used "popular" means to prolong a political career.[96]
His analysis viewedpopularis in terms of a method "adopted by those who opposed the senatorial majority, [providing] a behavioural model which did not concern itself with attributing motive to political action".[97] Gruen in the famousLast Generation of the Roman Republic in 1974 rejected the terms entirely:
The termoptimates identified no political group. Cicero, in fact, could stretch the term to encompass not only aristocratic leaders but also Italians, [farmers], businessmen, and even freedmen. His criteria demanded only that they be honest, reasonable, and stable. It was no more than a means of expressing approbation. Romans would have had even greater difficulty in comprehending the phrase "senatorial party"... The phrase originates in an older scholarship which misapplied analogies and reduced Roman politics to a contest between the "senatorial party" and the "popular party". Such labels obscure rather than enlighten.[19]
Brunt, writing in the 1980s–90s, took a view trending against political parties but towards an ideological dimension. He emphasised that shifting alliances and loyalties between senators precluded the existence of "durable or cohesive political factions"[98] which could be identified asoptimates orpopulares and that "optimates and populares did not and could not constitute parties as we know them".[99][100] Moreover, he argued there were no "large groups of politicians, bound together by ties of kinship or friendship, or by fidelity to a leader, who [acted] together consistently for any considerable time" and that "of large, cohesive, and durable coalitions of families there is no evidence at all for any period".[101] Instead, he argued that the distinction was not one of permanent factional strife, but rather, of support and opposition of the senate:popularis politicians, while not being "reformers" per se, would resort to the popular assemblies if they felt intervention from the people was desirable, with an ideological distinction dividing Roman politicians as to what was in the public interest.[100]
Theoptimates were explored by Burckhardt in 1988, viewing them as portions of the nobility acting to advance laws against corruption, electoral bribery, and overly flagrant displays of wealth (ie laws onrepetundae,ambitus, andsumptuaria) with tactics such as vetoes and obstructionism. Gruen, however, noted in 1995, that this analysis provided "no clear criteria" for determining anything about the makeup, size, or organisation of the group.[102] Identification ofoptimates also continues to be difficult. They have been identified as "members of an 'aristocratic party' to upholders of senatorial authority to supporters of the class interests of the wealthy".[103]
Mackie argued in a 1992 influential paper revitalising the ideological view thatratio popularis implied and required substantial argumentation based on Roman tradition to justify the intervention of the popular assemblies. Such argumentation took the form of an ideology of popular sovereignty, self-justifying the leadership of the comitia in the state.[104] Hölkeskamp suggested in 1997 thatpopularis ideology reflected a history of senatorial intransigence characterised as "partial and unlawful" which, over time, eroded the legitimacy of the senate in the republic.[105] Morstein-Marx's book on mass oratory in the republic – often beforecontiones or assemblies of the people – focused, however, on how both opponents and supporters of legislation attempted to portray themselves as "true"popularis acting in the interest of the people and the other as demagoguery.[106]
There continues to be debate as to the utility of the terms in scholarship. In 1994, Andrew Lintott wrote inThe Cambridge Ancient History that although both factions came from the same social class, there is "no reason to deny the divergence of ideology highlighted by Cicero" with themes and leaders stretching back in Cicero's time for hundreds of years.[107] T. P. Wiseman similarly lamented an "ideological vacuum" in 2009, promoting the term as a label for ideology rather than for political factionalism in the vein of Mommsen.[108]
Other recent publications have continued to contest the topic. M. A. Robb argued in her 2010 bookBeyond Populares and Optimates that the labels emerge from Cicero's writings and were "far from corresponding with definite parties or definite policies".[3] It seems Romans did not use the terms themselves: for example, Caesar and Sallust never identifiedCaesar as a member of anypopulares "faction".[3] "The termspopulares andoptimates were not common and everyday labels used to categorise certain types of late republican politician".[53] Robb rejects usage of bothpopulares andoptimates writ large, as all Roman politicians would have asserted their devotion to public liberty and also have asserted their own excellence; instead ofpopulares to describe demagoguery, Romans would have usedseditiosi.[109] Similarly, Henrik Mouritsen, writing in the 2017 bookPolitics in the Roman Republic rejects the putative categories entirely, supporting a "politics without 'parties'" in the vein of Meier, where politicians "at certain moments in their career[s] used their powers without the backing of their peers".[80]
^Mouritsen also cautions against viewing the senators as fiscal conservatives: Romans were not directly taxed and the tax system in general had no redistributive effect. Questions of tax policy revolved not on how much Romans should pay, but on how much non-Roman provincials should pay.[22]
^Mouritsen 2017, p. 116. "The revival of Mommsen's ideological model, albeit without the formal 'party' structures, coincides with the rise in 'democratic' interpretations of Roman politics, which it logically complements".
^Robb 2010, pp. 171–72. See note 27, citing Meier's observation that "the only identifying 'popularis' characteristic of Memmius' proposal was his decision to implement it in the face of senatorial opposition".
^Lintott, Andrew (1992)."Political history, 146–96 BC". In Crook, John; et al. (eds.).Last age of the Roman republic. Cambridge Ancient History. Vol. 9 (2nd ed.). Cambridge University Press. p. 52.ISBN978-0-521-25603-2.