The causes of the French Revolution were ideological, political, economic, social ones. The ideological cause that contributed to the outbreak of the revolution was the Enlightment, which was the period of new political, social, and philosophical ideas postulated by the 18th century French thinkers and writers such as Voltaire, Jean-Jacques Rousseau, Denis Diderot, and Montesquieu. François-Marie Arouet, known by the pen name of Voltaire, was an outspoken supporter of social reform and was famous for his advocacy of civil liberties and individual rights, including freedom of religion and free trade. Rousseau wrote the Discourse on the Origin of Inequality and The Social Contract, which were cornerstones in modern political and social thought; Rousseau´s Social Contract outlines the basis for a legitimate political order within a framework of classical republicanism; this treatise begins "Man was born free, and he is everywhere in chains. One man thinks himself the master of others, but remains more of a slave than they."
The political cause of the French Revolution: there were two antecedents of a republican system in which power was shared or divided and not concentrated in one absolute monarch; the Roman Republic which was governed by a complex constitution that centered on the principles of a separation of powers and checks and balances (Senate, Consuls, and Praetors); the emmancipation of the thirteen British colonies in North America led to the stablishment of a republican government in which power was divided into three branches: executive, legislative, and judicial. The American Constitution’s Bill of Right also had an influence on the French people.
The economic cause was the debt and the inequity (unfairness) of taxation. It was debt that led to the long-running fiscal crisis of the French government. On the eve of the revolution, France was effectively bankrupt. Extravagant expenditures on luxuries by Louis XVI and his wife Marie Antoinette were compounded by debts that were run up during the reign of his even-more-profligate predecessor, Louis XV, who reigned from 1715 to 1774. Heavy expenditures to conduct the losing Seven Years’ War against Britain (1756–1763), and France’s participation in the American War of Independence, which increased the debt even higher. Collections of taxes, such as the extremely unpopular salt tax, the gabelle, were contracted to private collectors ("tax farmers"), who, like all farmers, preoccupied themselves with making their holdings grow. So, they collected, quite legitimately, far more than required, remitted the tax to the State, and pocketed the remainder. These unwieldy systems led to arbitrary and unequal collection of France’s consumption taxes. Peasants were also required to pay a tenth of their income or produce to the church (the tithe), a land tax to the state, a 10% property tax, and a tax on the number of people in the family.
The social cause of the French Revolution arose out of the underlying social malaise and general dissatisfaction, which in turn was caused by the food scarcity of the 1780s. A series of crop failures caused a shortage of grain, due to extreme winter conditions, consequently raising the price of bread. Because bread was the main source of nutrition for poor peasants, this led to starvation. The two years previous to the revolution (1788–89) saw meager harvests and harsh winters. In 1789, a normal worker, a farmer or a laborer, earned anywhere from fifteen to thirty sous per day; skilled workers received thirty to forty. A family of four needed about two loaves of bread a day to survive. The price of a loaf of bread rose by 67 percent in 1789 alone, from nine sous to fifteen. Many peasants were relying on charity to survive, and they became increasingly motivated by their hunger.