The classic defence of negative liberty remains Isaiah Berlin's 'Two Concepts of Liberty', first published in 1958. Berlin defined 'being free' as "not being interfered with by others. The wider the area of non-interference, the wider my freedom." (Berlin, 1969, p. 123) This definition is a throwback to Hobbes' presentation of liberty in the Leviathan as the absence of 'external impediments'.
For Hobbes, "a free man, is he, that in those things, which he by his strength and wit he is able to do, is not hindered to do what he has a will to." (Hobbes, 1968, p.262) In Hobbes' view, these hindrances included the laws of the sovereign, framed after civil society had been created by the social contract, since liberty depended on the 'silence of the law'. The absence of civil laws in the state of nature should have translated into more freedom for its denizens, but in its very absence, every individual acted as an external impediment to another's freedom of action. By his laws the sovereign ensured that his citizens were free from interference from one another.
It is good to keep in mind here how Hobbes, one of the earliest advocates of negative liberty, saw no contradiction between the 'needful' laws of an absolute sovereign and his-subjects' liberty. To judge whether an individual was free, it was irrelevant to check whether she had any say in the laws under which she lived. The absolute sovereign alone made the laws. What was crucial was whether the sovereign left as large an area of her life as possible unregulated by his laws. Berlin makes the same point: liberty in its negative sense "is principally concerned with the area of control, not with its source...there is no necessary connection between individual liberty and democratic rule. The answer to the question 'Who governs me?' is logically distinct from the question 'How far does government interfere with me?" (Berlin, 1968, pp. 129-130)
In explaining the concept of liberty, Hobbes distinguished between freedom and ability: "But when the impediment of motion, is in the constitution of the thing itself, we can not say, it wants the Liberty, but the Power to move; as when a stone lies still, or a man is fastened to his bed by sickness." (Hobbes, 1968, p. 262) Most exponents of negative liberty echo this distinction between power or ability and liberty. What they disagree about is when a certain condition is to be characterised as a lack of ability and when as a lack of liberty. Not being able to fly because of a lack of wings is, in the case of human beings, a clear case of the lack of an ability, and not of being unfree.
But what about the case of a man who is too poor to afford "something on which there is no legal ban - a loaf of bread, a journey round the world." Berlin argues that given a social theory in which this poverty is the result of "other human beings having made arrangements" whereby some men lack material resources while others enjoy an abundance of them, the poor man should be described not as being unable to buy bread, but as being unfree to do so: "The criterion of oppression is the part that I believe to be played by other human beings, directly or indirectly, with or without the intention of doing so, in frustrating my wishes." ( See Berlin, 1968, pp. 123-4) This is certainly a far cry from the work of Hillel Steiner, according to whom, only physical barriers intentionally placed on someone's action can allow that person to claim that she is not free. We see then that there is a wide range in the understanding of what is to count as impediments/obstacles to action, even among the advocates of negative liberty.
Another classical defence of negative liberty was John Stuart Mill's 1859 essay, On Liberty. Here is Mill's position in brief: "...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...the only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant...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." (J.S. Mill, 1989, p. 13)
Insisting that there is a line, however faint, between self-regarding and other regarding action, Mill argued that the principle of liberty brooked no interference with the sphere of one's self-regarding action. Discussing three specific areas - of thought and its oral and written expression, of taste and pursuits, and of combination or association with other individuals - Mill claimed that except to prevent 'direct material harm' to others, society had no other justification for interfering with the liberty of the individual in these areas. "No society in which these liberties are not, on the whole, respected, is free, whatever may be its form of government, and none is completely free in which they do not exist absolute and unqualified." (J.S. Mill, 1989 p. 16).
For Mill, the goal of social theory was to further the improvement of mankind. Mill saw his contribution in showing the world that individual liberty is an essential means to this improvement: "… the only unfailing and permanent source of improvement is liberty, since by it there are as many possible independent centres of improvement as there are individuals." (J.S. Mill, 1989, p. 70) Mill explained this in the following terms: "The human faculties of perception, judgment, discriminative feeling, mental activity, and even moral preference, are exercised only in making a choice." (Mill, p. 59) But if the value of liberty is that it improves mankind, what is one to do with the possibility of individuals always choosing to act in wrongful ways in their sphere of self-regarding action? This brings us to the conception of positive liberty.