The essay argues for the primacy of individual development and sets out a general rule limiting social and governmental interference: power over a person is justified only to prevent harm to others. It defends freedom of thought, discussion, and expression as essential to truth and personal growth, warns against the tyranny of prevailing opinion, and upholds liberty in tastes, pursuits, and associations so long as they do not harm others. It also champions individuality and experiments in living as engines of social progress and examines practical boundaries between collective authority and personal autonomy.