Mill in On Liberty proposes a simple principle for determining whether society has a right to limit individual freedom, a principle based on utilitarian concepts and applicable to the individual in his or her dealings with society. That principle holds that the only thing of ultimate value is the happiness of individuals, and individuals can best achieve their happiness in a civilized society when they are left free to pursue their own interest with their own talents as these have come to be understood and developed by them under an adequate system of education. Mill thus asserts the principle of non-interference where the individual is concerned, though this applies only to adults and not to children.
Mill bases his idea on the self-development of the individual. He does not, however, base this idea on any sense that there is a natural right on the part of the individual to develop himself freely, and instead he bases it on the principle of utility. This principle says that each individual should be free to develop his or her own powers and abilities according to his or her will or judgment as long as they do so in a way that does not interfere with the rights of others. From the standpoint of society, says Mill, this is also desirable because it is preferable that individuals develop themselves freely since this enhances society, while having everyone conform does not. The free development of the individual is one of the principal ingredients of human happiness, and therefore it is a utility for the individual to develop himself freely as a way of achieving that happiness.
Mill states that there is a necessity for the mental well-being of mankind and that it depends on two things--freedom of opinion, and freedom of the expression of opinion. Each person has the right to his or her own opinion, and society has no right to squelch this opinion any more than the individual would have the right to squelch that of all manki...