As the Labour Party prepares for its annual conference Huw Richards asks what the ingredients are for good leadership.

"The problem of just what was meant by 'a good government' lay at the very heart of political theory. Perhaps it always does." So wrote historian David Thomson on the thought of Jean-Jacques Rousseau in 1966.

Thomson was looking back over two centuries to Rousseau's era (1712-67). But few historians or political theorists today would detract from Thomson's viewpoint. No matter what your criterion - whether "good", "effective" or "successful" government - judgement is almost unavoidably subjective. Ask the most rigorous British observer to rank the administrations of Herbert Asquith, Clement Attlee, Winston Churchill, Anthony Eden, Harold Macmillan or Margaret Thatcher, or get their US counterpart to perform a parallel exercise on the presidencies of Franklin Roosevelt, Dwight Eisenhower, Ronald Reagan and Bill Clinton, and the outcome is likely to tell you more about them than about those governments.

As Joseph Nye, founding father of Harvard's Visions of Governance project, the most extensive contemporary study of government, wrote in 1997: "Purely neutral government is impossible, because citizens want some discussion of what is good." The question of what makes good government cuts across the, in any case ill-defined, border between history and political science. Political science, with its more theoretical bent, has tended to approach it more directly, while the historiography is addressed more through implication than frontal assault.

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Government's most assiduous recent chronicler, S. E. Finer, author of a three-volume History of Government (1997), notes that conceptions, expectations and models of government changed dramatically over time. While dating the earliest forms of government to Sumeria between 3200BC and 3500BC, he quoted approvingly Jean Dunbabin's comment, in her 1985 study of medieval France, that "nobody was governed before the late 19th century. It would certainly be foolish to maintain that either royal or princely government in the 12th century operated according to fixed rules or over all the inhabitants of a fixed area."

Finer defined five characteristics of a state: a territorially defined population recognising a common authority; specialist bureaucratic and military personnel; recognition as sovereign by other states; a self-conscious common identity; and a population participating in the distribution and sharing of duties and benefits. He noted that both self-conscious identity - which he reckoned emerged in England in the 13th century, France 200 to 300 years later and Spain as late as the 18th century - and popular participation emerged much later than the other characteristics.

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In addition, he noted four essential activities: defence, which he characterised as "primordial" in that a polity that cannot defend itself has by definition failed; law, order and justice; taxation, although he noted that the Holy Roman Empire had no central treasury or chancery; and the "highly subjective territory" of public works and welfare.

In analysing change, Finer noted that, until comparatively recently, states were regarded as the property of a ruler chosen by divine right, and pointed out that while the Athens of Plato and Aristotle has been regarded as the starting point of political development, the autocratic militarism of Sparta provided the dominant form of government in the West until the late 18th century, with individuals more likely to be subjects than citizens.

The most prominent thinkers on government have been products of their times. Italy's fratricidal wars informed the subtle mind of 15th-century writer Niccol Machiavelli, whose enduring appeal rests on tough-minded realpolitik - recommending, for instance, that "men should be either treated generously or else destroyed, because they take revenge for slight injuries, for heavy ones they cannot" - and an elegantly epigrammatic style. He argued for the fundamental importance of military strength ("where there are good arms, good laws invariably follow") and for the supremacy of raison d'¨¦tat ("putting aside every other consideration, one ought to follow to the end whatever will save the life of the state and preserve its freedom").

Similarly, the belief of Thomas Hobbes (1588-1679) in the right of the state to impose order to curb man's inherently aggressive nature - the alternative being a state of nature in which life was, in his most famed phrase, "nasty, brutish and short" - doubtless owed something to the Civil War concluded two years before the publication of his major work Leviathan .

John Locke (1632-1704), epitomising an era that deposed Charles I and his son James II, devised both a fatal challenge to the doctrine of divine right and one of the basic criteria for defining unsuccessful government. He developed the concept of consent on the basis of contract between ruler and ruled, arguing that "inconstant, uncertain, unknown and arbitrary government" forfeited consent.

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Much subsequent thought was devoted to consent and legitimacy - the ideas espoused by Jean-Jacques Rousseau (1712-67) and Thomas Paine (1737-1809), reaching a logical conclusion in France's Declaration of the Rights of Man and of the Citizen of 1789: "Sovereignty resides in the people; it is one and indivisible, imprescriptible and inalienable." Neither Paine nor Rousseau, both concerned with human and property rights, intended some of the consequences that flowed from an indivisible concept of property.

Many leading 19th-century thinkers devoted themselves to the balance between individual and collective rights. Benjamin Constant (1767-1830) argued, "there is a part of human life which necessarily remains individual and independent, and has the right to stand outside social control", while Jeremy Bentham (1748-1832), best remembered for his proposition that policy should serve "the greatest good of the greatest number", argued that governments needed to create "continuity and predictability", enabling citizens to "form a general plan of conduct".

Finer argues that the decisive development for modern government was industrialisation, which transformed its income-generating and collecting potential, its powers of supervision and surveillance, and created an industrial working class whose demands created pressure for greater intervention in economic and social policy. While the social democratic parties that then emerged were often Marxist in rhetoric, in practice they tended to be followers of Eduard Bernstein (1850-1932), who argued forcibly that the German Social Democratic Party could best achieve its aims by working within existing political structures and, where necessary, cooperation with middle-class liberals.

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Universal suffrage in Britain ushered in an age that broadly accepted the view expressed by William Beveridge in 1942 that "the object of government in peace and war is not the glory of rulers or of races, but the happiness of the common man", even if there was disagreement on how to achieve this.

Hence the expansion of social welfare programmes after the Second World War, and of political priorities most crisply expressed in the "it's the economy, stupid" catchphrase used by the successful Clinton presidential campaign of 1992. However anti-government their ideology, conservative politicians have accepted that economic and social welfare is the central concern of politics.

But these developments have been accompanied, particularly in the US, by declining faith in the efficacy of government. Management thinker Peter Drucker argued in 1969 that "the greatest factor in the disenchantment with government is that government has not performed", a view in essence endorsed in David Osborne and Ted Gaebler's Reinventing Government , an influential text for market-minded centre-left politicians such as Al Gore and Tony Blair. Derek Bok, president of Harvard University until 1991, has concluded that the US has probably not been as well run as other "leading democracies" since 1960, but adds a rider: "To someone who feels that economic growth or poverty and social justice matter more than anything else, it may appear that the country has gone into decline since the 1970s.

Conversely, to those who feel especially strongly about the environment, crime or personal responsibility, America will seem to be doing somewhat better than in the early 1970s, but not as well as it should."

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In other words, successful government is in the eye of the beholder. As the writers of that most penetrating study of government Yes, Minister might have observed, the invariable problem with beholders is that "I am principled, you are an ideologue, he is a mindless fanatic".