Final answer:
John Green discusses 'revolutionary ideas' from the Enlightenment era that contributed to significant social and political transformations. These include democracy, social equality, individual liberty, freedom of speech, education for all, gender equality, and abolition of slavery.
Step-by-step explanation:
The question asks about John Green's mention of ‘revolutionary ideas’. These ideas primarily revolve around the philosophical movement known as the Enlightenment, which brought about significant social and political changes. The Enlightenment introduced critical skepticism toward traditional authorities and posited the importance of reason, scientific method, and the idea of human progression and improvement of society.
Some of the ‘revolutionary ideas’ mentioned by John Green include democracy, the concept of social equality, the notion of individual liberty, freedom of speech, and the critique of divine right monarchy. John Locke and Jean-Jacques Rousseau, for instance, contributed to the idea of a social contract, which promotes the protection of individual freedoms. Additionally, Enlightenment thought influenced movements that advocated for education for all, gender equality, and the abolition of slavery. These ideas were instrumental in shaping modern democratic institutions, fostering the notion of human rights, and prompting revolutions like those in America, France, and Haiti.