Simplify the following text for a Grade 10 native English-speaking person.
Original: So , in a more complex way , did Jean-Jacques Rousseau , whose notions centered on the goodness of man and the liberty of citizens bound only by the social contractâ '' a form of popular sovereignty .
Simplified: So , in a more complex way , did Jean-Jacques Rousseau , whose notions centered on the goodness of man and the liberty of citizens bound only by the social contract .