呢本書旨在撐好簡單嘅原則，有權徹底控制社會點樣管人，唔理用法律刑罰，定輿論道德。條原則係，無論單獨定集體，干預人哋自由做嘢，惟一合理目的，係自衛。以權力違背文明人意願，惟一合理目的，係防止傷害其他人。爲佢好，唔理爲身體，定爲品行着想，都唔係充足理由。唔可以逼佢做抑或唔做，就算咁會對佢好啲，或者會令佢開心啲，或者人哋覺得，咁係明智，或者直程係啱。呢啲係好理由，用蒞鬧佢、勸佢、說服佢，或者懇請佢，但唔係用蒞迫佢、害佢，或者阻佢做相反嘅嘢。要證明阻得啱，要阻嘅事要係特登害人。人所作所爲，牽涉其他人，先要向社會交代。淨係影響自己，人絕對有權自己話事。對自己又好，對自己身心又好，自己係話事人。
The object of this Essay is to assert one very simple principle, as entitled to govern absolutely the dealings of society with the individual in the way of compulsion and control, whether the means used be physical force in the form of legal penalties, or the moral coercion of public opinion. That principle is, that the sole end for which mankind are warranted, individually or collectively, in interfering with the liberty of action of any of their number, is self-protection. That the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant. He cannot rightfully be compelled to do or forbear because it will be better for him to do so, because it will make him happier, because, in the opinions of others, to do so would be wise, or even right. These are good reasons for remonstrating with him, or reasoning with him, or persuading him, or entreating him, but not for compelling him, or visiting him with any evil in case he do otherwise. To justify that, the conduct from which it is desired to deter him, must be calculated to produce evil to some one else. The only part of the conduct of any one, for which he is amenable to society, is that which concerns others. In the part which merely concerns himself, his independence is, of right, absolute. Over himself, over his own body and mind, the individual is sovereign.
