Revolutions- the overthrows of rulers or systems of government- are generally caused by a combination of weakness or divisions within the ruling establishment, combined with dissatisfaction among various other segments of the population.
Many of the revolutions in history have been led by members of the lower strata of the elite, or dissidents within the elite. In other words, people who are somewhat privileged compared with other groups in society, but who are not part of the top ruling elite. Or, privileged people who are, for some reason, unhappy with the top ruling circle. If these people are able to win the support of a large segment of the population, then their revolutions have the greatest chance of success. If, on the other hand, they are unable to win popular support, then their revolutions are less likely to succeed.
The French Revolution, for example, was initially precipitated by the opposition of some segments of the aristocracy to royal absolutism. Later on, the wealthier, more educated, and privileged commoners- the middle classes and bourgeoisie- emerged as the leaders of the revolution. But the success of the French Revolution was largely due to the fact that the opponents of the king enjoyed a great deal of popular support.
So, for example, when King Louis XVI, and his ministers, tried to forcibly impose changes to the tax system to avert bankruptcy, they faced opposition from the aristocratic judges who sat of the Parlement (high court) of Paris. The aristocrats argued that in order to make such drastic changes to the tax system, Louis would have to call on a representative body called the Estates General. When Louis XVI tried to have his aristocratic opponents exiled, and unilaterally impose the changes, there were mass uprisings across the country. The violence scared lenders, who became unwilling to provide further loans to the nearly bankrupt French government. So, because of the popular support for the aristocratic dissidents, Louis was forced to call up the representative Estates General to approve his changes to the tax system.
Similarly, when Louis XVI tried to re-establish absolute rule by shutting down the Estates General, the common people again saved the king’s opponents. When Louis XVI sent his armies to shut down the Estates General by force, the people of Paris armed themselves and prepared to defend their city from the royal army. The famous Storming of Bastille in 1789 was carried out in order to gain access to weapons, and gunpowder stored inside the Prison. When Louis XVI realized that the people were armed, and ready to fight, he abandoned his attempts to forcibly shut down the Estates General. The populous had once again saved the king’s aristocratic, and bourgeois opposition from being crushed.
More privileged revolutionaries often provide specific ideological motivations for their revolutions. For example, the slogan commonly attributed to middle-class French revolutionaries was “liberté, égalité, fraternité” (liberty, equality, and brotherhood). The Declaration of the Rights of Man is another well-known ideological work that came out of the French Revolution. Other ideologies were associated with other revolutions. Russian revolutionaries adhered to socialist, communist, and anarchist ideologies. Communism and socialism became popular revolutionary ideologies after the end of the Second World War.
Among the poorest and least educated segments of society, motivations for revolutionary activity are often more practical, and straight forward. During the French Revolution the scarcity of affordable staple foods, such as bread, motivated the mobs of Paris. In Russia the downfall of the Tsarist regime was precipitated by the deprivations associated with the First World War.
Another factor in revolutions are weaknesses within the ruling system. The French Revolution was precipitated by France’s imminent bankruptcy, caused by years of heavy spending with an inadequate tax system. The Tsarist government of Russia collapsed under the strain of attempts to fight a major modern war with an outdated system of communications, and administration. The archaic imperial government of China collapsed in the early twentieth century under the strain of domestic and foreign pressures.
Summary:
Revolutions are typically caused by a combination of weaknesses or power disputes within the ruling elite, combined with popular dissatisfaction. Members of the lower strata of the elite may resent their exclusion from the top ranks and decision making of the ruling circle. The middle-class revolutionaries of late 18th century France, the middle-class protesters of Vietnam War era United States, many of the communist revolutionary leaders in Russia, China, Asia, Africa, and Latin America in the 20th century, colonial elite Anglo-American rebel leaders such as George Washington, many of the leaders of the independence movements in the European colonies of Africa and Asia, the leaders of early 19th century Spanish-American revolutions, and others, all belonged to this lower strata of the elite.
Lower segments of the population will often turn to violence if their basic needs are not met. For example, food shortages precipitated uprisings in revolutionary era Paris, World War I era Russia and Germany, and in Qing China.
A third factor in revolutions are the weaknesses of ruling regimes. In some cases ruling systems are ineffective, corrupt, or archaic, which facilitates their downfall when faced with elite or popular opposition.
Reference:
King Louis XVI of France
http://www.helium.com/items/2231449-biography-king-louis-xvi
Causes of the Russian Revolution of 1917
http://www.helium.com/items/1960218-causes-of-the-russian-revolution-of-1917
The Decline of China’s Qing (Manchu) Dynasty
http://www.helium.com/items/2165455-the-decline-of-chinas-qing-dynasty
Ways the American Revolution Was Similar to the French Revolution:
http://www.helium.com/items/2109068-ways-the-american-revolution-was-similar-to-the-french-revolution
The Causes of the French Revolution:
http://www.helium.com/items/2002267-french-history-the-causes-of-the-french-revolution