Here are some key concepts and ideas from "On Liberty":Harm Principle: Mill introduces the "harm principle," which asserts that the only justification for limiting an individual's freedom is to prevent harm to others. This principle sets the boundary for the legitimate scope of government intervention, allowing individuals to pursue their own happiness and make their own choices as long as they do not harm others.Freedom of Thought and Expression: Mill strongly advocates for the freedom of thought and expression, even when the ideas being expressed are controversial or unpopular. He believes that the open exchange of ideas, even those deemed offensive or false by society, is essential for the discovery of truth and the growth of knowledge.Individuality and Diversity: Mill emphasizes the importance of individuality and diversity in society. He argues that suppressing individuality leads to stagnation and conformity, whereas a society that values individual expression and unique perspectives is more likely to make progress and foster human development.Tyranny of the Majority: Similar to his concerns in "Considerations on Representative Government," Mill warns against the "tyranny of the majority." He cautions that a majority, even in a democratic society, can impose its views on the minority, stifling dissent and hindering progress. Protection of minority rights is essential to prevent such tyranny.