Liberty  -  For Mill, liberty encompasses both civil and social liberty, which he defines as "the nature and limits of the power of which can be legitimately exercised by society over the individual." Mill argues that society can only exert authority over behavior that harms other people, anything else is an abrogation of individual freedom.

Tyranny of the majority  -  This is the concept that in a democratic state the majority of people can impose its will on a minority. Mill believes this behavior is "tyrannical" when it violates a claim that the minority has as a member of society.

Social Contract  -  This reflects the idea that society is something that people either explicitly or implicitly agreed to be part of. Social contract theory was first formulated by Rousseau in The Social Contract, and defines rights as those things that people would have agreed to have protected by society, and duties as those things people would have agreed to take on as obligations, had they been present at the formation of the state.

Infallible  -  Incapable of making a mistake or being wrong.

Fallible  -  Capable of making mistakes and being wrong.