Why did John Stuart Mill oppose paternalistic laws that controlled adults for their own good?

John Stuart Mill opposed paternalistic laws that controlled adults for their own good primarily because he believed that individuals are the best judges of their own interests. In his seminal work, On Liberty, Mill argued that the only legitimate reason for society or government to interfere with an individual's liberty against their will is the harm principle—to prevent harm to others.123

Mill’s opposition was rooted in several key moral and utilitarian arguments:

• Respect for Autonomy: He contended that paternalism treats adults like children, failing to respect their capacity to determine and pursue their own well-being.12
• Human Development: Mill believed that a state that restricts personal choice to enforce a person's "own good" ultimately "dwarfs its men," hindering the development of individual character and speculative intelligence necessary for a progressive society.4
• Utilitarian Grounds: He argued that individual liberty is essential for the "greatest happiness of the greatest number," as the free play of mind and the collision of diverse opinions are vital for discovering truth and fostering social progress.234

Consequently, Mill maintained that an individual's physical or moral well-being is not a sufficient warrant for state interference.2