Final answer:
The most celebrated manifestos in Western Civilization emphasize the ideas of liberty and equality, central to democratic thought and prominent during significant historical periods like the Enlightenment and the French Revolution.
Step-by-step explanation:
The two ideas about society that were written about in the most celebrated manifestos in Western Civilization are liberty and equality. These ideas are seminal to democratic ideologies and have been a persistent theme throughout historical discourse, including during the Enlightenment and the French Revolution. The concept of liberty pertains to the ability to act freely within the confines of societal rules and law, while equality deals with the idea that all individuals are entitled to the same rights and opportunities without discrimination.