The nature and limits of the power which can be exercised by society over the individual.
The struggle between liberty and authority is the most conspicuous feature in history. In old times, this was a contest between subjects and the government. Rulers were conceived as necessarily antagonistic towards the people they ruled. Government consisted of a tribe or governing class that derived authority from inheritance or conquest. They did not hold authority at the pleasure of the governed, and there was little desire to challenge their supremacy, though precautions may be taken against oppression. This power was regarded as necessary, but also dangerous, as it could be used against subjects as well as enemies.
To prevent weaker members of the community from being preyed upon by innumerable vultures, it was needful that there should be an animal of prey stronger than the rest, commissioned to keep them down. Given however that this king was no less likely to prey on the flock than the lesser threats, a perpetual defense against him was necessary too.
The aim was then to set limits to the power which the ruler could exercise over the community, and this limitation was what they meant by liberty. This was accomplished in two ways: first by obtaining recognition of certain immunities, called political liberties, or rights. The second- the establishment of constitutional checks, followed later. This meant that the consent of the governed was made a necessary condition to the governing power. This held as long as men were content to combat one enemy by another- to be ruled by one master on condition of being guaranteed against his tyranny.

In time though, men came to think that the governing power should be themselves, rather than an independent power. Politicians of state should be their tenants, revocable at their pleasure. As this democratic mindset took hold, some began to think limiting power was unimportant, since the limitation was to keep the rulers in check. But if the people were now the rulers, they didn’t need to be protected against their own will, since there was no fear of tyrannizing itself.

However, success discloses faults and infirmities which failure might have concealed from observation. The need to loosen the limits of restriction on power seemed reasonable as long as their power was only theoretical. Elective government, once enabled and seen in action, began to manifest a fact: self-government and the power of the people do not express the true state of things. The ‘people’ who exercise the power are not always the same people over who it is exercised. The ‘will of the people’, in practice, means the will of the most numerous, or most active part of the people. The limitation of the power of government over individuals is still important when those that hold power are accountable to the strongest party therein. The term is the tyranny of the majority, by what is meant the power of majorities to inflict upon minorities, and it is a power which needs to be guarded against.
The tyranny of the majority was at first chiefly operating through acts of public authorities. But reflective persons can perceive that society collectively can be the tyrant over individuals who compose it. When society executes it’s own mandates it practices a social tyranny more formidable than political oppression. Protection then against the tyranny of the magistrate is not enough; there needs to be protection against the tyranny of the prevailing opinion and feeling.

Let’s suppose however, that the government is entirely at one with the people, and never thinks of exerting any power of coercion unless in agreement with what it conceives to be their voice. I still deny the right because the power is itself illegitimate.
First, the opinion which it is attempted to suppress by authority may possibly be true. Those that try to suppress it may deny it’s truth; but they aren’t infallible. They have no authority to decide the question for all mankind and exclude every other person from the means of judging. All silencing of discussion is an assumption of infallibility.
Nearly everyone accepts that are fallible, but few think it necessary to take any precautions against their own fallibility, or admit the supposition that any opinion of which they feel very certain, may be one of the examples of the error to which they acknowledge themselves to be liable.

The objection to this argument will be that there is no greater assumption of infallibility in forbidding the propagation of error than in anything else done by public authority on it’s own judgment and authority. If we were to never act on our opinions because we may possibly be wrong, we couldn’t act on anything. Therefore we must assume our opinion to be true for the guidance of our own conduct.
But it is assuming much more! There is a great difference between presuming an opinion to be true because with every opportunity of contesting it, it has not been refuted, and assuming it’s truth for the purpose of not permitting it’s refutation. Complete liberty of contradicting and disproving our opinion is the very condition which justifies us in assuming its truth for purposes of action; and on no other terms can a human being have any rational assurance of being right.