Final answer:
Members of the Third Estate were discontent with the old regime because they were burdened with high taxes and economic hardships while the privileged estates were exempt. This inequity in the social and economic structures of French society, compounded by an unfair voting system, led to the formation of the National Assembly and sparked the French Revolution.
Step-by-step explanation:
Causes of the Third Estate's Discontent Under the Old Regime
The discontent of the Third Estate in France prior to the French Revolution had several causes rooted in the longstanding social and economic inequalities of the time. The Third Estate, making up approximately 97% of the population, bore the brunt of taxation while the First (clergy) and Second (nobility) Estates, who were the minority, enjoyed various privileges, including exemption from most taxes. The Estates General of 1789 brought these issues to the fore when it became clear that the archaic voting system would not allow the Third Estate's grievances to be addressed fairly since each estate had one vote, thus the combined clergy and nobility could outvote the commoners.
With France on the brink of bankruptcy due to extravagant royal spending and the costs of supporting the American Revolution, the Third Estate found themselves suffering from poor harvests, high food prices, and harsh taxes. Resentment festered as the clergy and nobility seemed indifferent to the plight of the peasants and urban poor. Inspired by Enlightenment ideals, the Third Estate sought to restructure the political and social order through the formation of the National Assembly and the drafting of a new constitution, all of which culminated in the revolution marked by the storming of the Bastille and widespread riots.