What were the causes of french revolution ?

Cultural: The Enlightenment philosophy desacralized the authority of the monarchy and the Catholic Church, and promoted a new society based on reason instead of traditions.
Social: The emergence of an influential bourgeoisie which was formally part of the Third Estate (commoners) but had evolved into a caste with its own agenda and aspired to political equality with the clergy (First Estate) and the aristocracy (Second Estate).
Financial: France's debt, aggravated by French involvement in the American Revolution, led Louis XVI to implement new taxations and to reduce privileges.
Political: Louis XVI faced strong opposition from provincial parlements which were the spearheads of the privileged classes' resistance to royal reforms.
Economic: The deregulation of the grain market, advocated by liberal economists, resulted in an increase in bread prices. In periods of bad harvests, it would lead to food scarcity which would prompt the masses to revolt.