Class conflict
Kirkus Reviews wrote: "Populist historian Parenti... views ancient Rome's most famous assassination not as a tyrannicide but as a sanguinary scene in the never-ending drama of class warfare."

Coriolanus: The patrician Coriolanus, whose life William Shakespeare would later depict in the tragic play Coriolanus, fought on the other side of the class war, for the patricians and against the plebs. When grain arrived to relieve a serious shortage in the city of Rome, the plebs made it known that they felt it ought to be divided amongst them as a gift, but Coriolanus stood up in the Senate against this idea on the grounds that it would empower the plebs at the expense of the patricians.
This decision would eventually contribute to Coriolanus's undoing when he was impeached following a trial by the tribunes of the plebs. Montesquieu recounts how Coriolanus castigated the tribunes for trying a patrician, when in his mind no one but a consul had that right, although a law had been passed stipulating that all appeals affecting the life of a citizen had to be brought before the plebs.
In the first scene of Shakespeare's Coriolanus, a crowd of angry plebs gathers in Rome to denounce Coriolanus as the "chief enemy to the people" and "a very dog to the commonalty" while the leader of the mob speaks out against the patricians thusly:

They ne'er cared for us yet: suffer us to famish, and their store-houses crammed with grain; make edicts for usury, to support usurers; repeal daily any wholesome act established against the rich, and provide more piercing statutes daily, to chain up and restrain the poor. If the wars eat us not up, they will; and there's all the love they bear us.

Landlessness and debt: Enlightenment-era historian Edward Gibbon might have agreed with this narrative of Roman class conflict. In the third volume of The History of the Decline and Fall of the Roman Empire, he relates the origins of the struggle:[T]he plebeians of Rome [...] had been oppressed from the earliest times by the weight of debt and usury; and the husbandman, during the term of his military service, was obliged to abandon the cultivation of his farm. The lands of Italy which had been originally divided among the families of free and indigent proprietors, were insensibly purchased or usurped by the avarice of the nobles; and in the age which preceded the fall of the republic, it was computed that only two thousand citizens were possessed of an independent substance. Hegel similarly states that the 'severity of the patricians their creditors, the debts due to whom they had to discharge by slave-work, drove the plebs to revolts.' Gibbon also explains how Augustus facilitated this class conflict by pacifying the plebs with actual bread and circuses.
The economist Adam Smith noted that the poor freeman's lack of land provided a major impetus for Roman colonisation, as a way to relieve class tensions at home between the rich and the landless poor. Hegel described the same phenomenon happening in the impetus to Greek colonisation.

Enlightenment era: Writing in pre-capitalist Europe, the Swiss philosophe Jean-Jacques Rousseau and the Federalist statesman James Madison across the Atlantic Ocean made significant remarks on the dynamics of class struggle. Later, German idealist Georg Wilhelm Friedrich Hegel would also contribute his perspective to the discussion around class conflict between employers and employees.

Jean-Jacques Rousseau: It was with bitter sarcasm that Rousseau outlined the class conflict prevailing in his day between masters and their workmen: You have need of me, because I am rich and you are poor. We will therefore come to an agreement. I will permit you to have the honour of serving me, on condition that you bestow on me the little you have left, in return for the pains I shall take to command you.
Rousseau argued that the most important task of any government is to fight in class warfare on the side of workmen against their masters, who he said engage in exploitation under the pretence of serving society. Specifically, he believed that governments should actively intervene in the economy to abolish poverty and prevent the accrual of too much wealth in the hands of too few men.

Thomas Jefferson: Thomas Jefferson (1743–1826) led the U.S. as president from 1801 to 1809 and is considered one of America's Founding Fathers. Regarding the interaction between social classes, he wrote:

I am convinced that those societies (as the Indians) which live without government enjoy in their general mass an infinitely greater degree of happiness than those who live under the European governments. Among the former, public opinion is in the place of law, & restrains morals as powerfully as laws ever did anywhere. Among the latter, under pretence of governing they have divided their nations into two classes, wolves & sheep. I do not exaggerate. This is a true picture of Europe. Cherish therefore the spirit of our people, and keep alive their attention. Do not be too severe upon their errors, but reclaim them by enlightening them. If once they become inattentive to the public affairs, you & I, & Congress & Assemblies, judges & governors shall all become wolves. It seems to be the law of our general nature, in spite of individual exceptions; and experience declares that man is the only animal which devours his own kind, for I can apply no milder term to the governments of Europe, and to the general prey of the rich on the poor.

James Madison: In his Federalist No. 10, James Madison revealed an emphatic concern with the conflict between rich and poor, commenting that "the most common and durable source of factions has been the various and unequal distribution of property. Those who hold and those who are without property have ever formed distinct interests in society. Those who are creditors, and those who are debtors, fall under a like discrimination." He welcomed class-based factions into political life as a necessary result of political liberty, stating that the most important task of government was to manage and adjust for 'the spirit of party'.

Georg Wilhelm Friedrich Hegel: In his Philosophy of Right, Hegel expressed concern that the standard of living of the poor might drop so far as to make it even easier for the rich to amass even more wealth. Hegel believed that, especially in a liberal country such as contemporary England, the poorest will politicise their situation, channelling their frustrations against the rich:Against nature man can claim no right, but once society is established, poverty immediately takes the form of a wrong done to one class by another.

Capitalist societies: Class conflict is most commonly described as occurring within capitalist societies. The conflict manifests itself as clashes between the capitalist class and working class, and takes the form of disputes over hours of work, amount paid in wages, division of profits, culture in the workplace, cost of consumer goods, cost of rent, control over parliament or government bureaucracy, and economic inequality. Even a seemingly benign humanitarian program such as government-provided disaster relief can exacerbate class conflict if the relief is seen as being unequally distributed depending on the recipient's class.

Adam Smith: 

Inequality in the distribution of wealth: Like Rousseau, the classical liberal Adam Smith believed that the amassing of property in the hands of a minority naturally resulted in a disharmonious state of affairs. He said that "avarice and ambition in the rich, in the poor the hatred of labour and the love of present ease and enjoyment, are the passions which prompt to invade property", requiring a government to protect property rights:Wherever there is a great property, there is great inequality. For one very rich man, there must be at least five hundred poor, and the affluence of the few supposes the indigence of the many. The affluence of the rich excites the indignation of the poor, who are often both driven by want, and prompted by envy to invade his possessions. It is only under the shelter of the civil magistrate, that the owner of that valuable property, which is acquired by the labour of many years, or perhaps of many successive generations, can sleep a single night in security. He is at all times surrounded by unknown enemies, whom, though he never provoked, he can never appease, and from whose injustice he can be protected only by the powerful arm of the civil magistrate, continually held up to chastise it.Writing The Wealth of Nations, Smith's concern was the welfare of the ordinary workers who make up society and provide for it:No society can surely be flourishing and happy, of which the far greater part of the members are poor and miserable. It is but equity, besides, that they who feed, clothe, and lodge the whole body of the people, should have such a share of the produce of their own labour as to be themselves tolerably well fed, clothed, and lodged.
Regarding the extravagant consumption of the aristocracy, he remarked that:All for ourselves, and nothing for other people, seems, in every age of the world, to have been the vile maxim of the masters of mankind.