How about;
John Stuart Mill-On Liberty.
The text directly concerns the position of the individual to the state, and thus society, examining issues such as free speech. Written c.1859, which fits well into the relevant period.
Jeremy Bentham's 'Utilitarianism' could also be useful, influencing Mill, and proposing an ethical doctrine 'the happiness of the greatest number'.
Hmm.. Possibly Karl Marx & Friedrich Engels-The Communist Manifesto?