The causes of the French Revolution, being provoked by this collision of the powers of the rising bourgeoise and an sinking aristocracy defending its privileges, was the Financial debt of the government and the long-standing political differences in the government. Over the course of twenty-five years after the Seven Years' War, the government of France could not manage it's finances on a sound basis. This was worsened when France aided the American Revolution against Great Britain. The Government had reached great financial debt. The problem lied and continued because of the government's inability to tap the wealth of the French nation by taxation. There was a great paradox in France being a rich nation with a government in poverty.
The deteriorating finances of the government is what triggered the prolonged differences between the Bourgeoisie and the aristocracy. The political differences between the monarchy and the nobles came about after the Seven Years' war also. The increasing debt of the government escalated the hope for the monarchy to resume a "absolute power" status along with Louis XIV. This could not be accomplished because of the doubt that the public had towards the present kings Louis XV and Louis XVI, and the public could not be swayed to help. The only result of the attempts for absolutism by the monarchy were a series of new and increase taxes on the nobles. The aristocracy immediately reacted to these taxes as declaring them unfair and would not accept them. Louis XV began with a series of Financial advisors chancellors which all had the intention of saving the monarchy from financial ruin.
They made many attempts at taxation, such as a land tax, but each of these were defeated by the nobles -- the Parlements were even destroyed for a brief time, but were later restored by Louis XVI in attempt to gain public support. The government continued to become poorer and poorer and it seemed the only successful taxation was done towards the peasants, whom had the least money. The monarchy eventually fell and caused great unrest leading to the French Revolution.
The French Revolution was caused by the escalating rivalry between the monarchy and the aristocracy. The conflict would make an impact on all of Europe to come and even world history. All this turmoil was caused by a bunch of greedy Nobles and kings which wanted power and money.