What did John Stuart Mill passionately defend in his work "On Liberty"?

Freedom of expression, including freedom of thought and discussion

The correct answer is Option 1 - Freedom of expression, including freedom of thought and discussion.

John Stuart Mill, a political thinker and an activist in the nineteenth century Britain, offered a passionate defence of freedom of expression, including freedom of thought and discussion. In his book On Liberty he offered four reasons why there should be freedom of expression even for those who espouse ideas that appear ‘false’ or misleading today.