A Brief History of Time by Stephen Hawking is one of the most bought and possibly least read of scientific popularisations. In what sense it was a history of time is also unclear, good title though it is. Is it a history of the study of time, or is it that potentially paradoxical thing, a history of the very framework which makes history possible? (Maybe it is just that particular rock on which Hawking's boat eventually foundered.)

However an unintended side effect of Hawking's best-seller is that ‘brief histories’ have since multiplied, as a glance at Amazon will confirm. Latest to enter the ranks is a whole series of philosophical brief histories, being published by Wiley-Blackwell, described in the blurb as a series of ‘narratives’ for (or is it of?) ‘those concepts which have had a profound effect on philosophical development and human understanding’. First up for philosophical brief histories are happiness and liberty, with justice and the soul in prospect, though whether anyone will dare to do another brief history of time remains to be seen.

In A Brief History of Liberty by David Schmidtz and Jason Brennan (Wiley-Blackwell, 2010) the historical approach works rather well. For instead of discussing the ideal of liberty in a top-down, abstract manner, Schmidtz and Brennan consider how liberty has developed in various areas over the centuries, focusing particularly on those institutions and arrangements which seem to them to have fostered liberty. Disclaiming knowledge of what an ideal society would look like, they look at the actual development of the rule of law, of religious freedom, of commercial freedoms and of civil liberties. Apart from rooting what they have to say in the real world, as opposed to developing Rawls-type definitions and thought experiments, one benefit of this approach is that it allows our authors to present an interesting case for eroding the classic distinction between negative and positive liberties. According to Schmidtz and Brennan, negative liberty is not only the precondition for the positive ability to run one's own life; by removing interference and obstacles from individuals' exercise of freedom and in giving them the material means to make their own choices, it also fosters in them attitudes conducive to the exercise of positive liberty. To put it programmatically, less dependence means more responsibility and control for the individual. One advantage of the historical approach is that Schmidtz and Brennan are able to show how this has actually been borne out in history, as negative liberties have increased.

In Schmidtz and Brennan's hands this turns out to be in part a defence of market societies: in contrast to less free arrangements, market societies have made ‘people of all classes wealthy enough to do more with their lives that would otherwise have been possible’. They are particularly critical of well-meaning attempts from the top to control distribution of various goods (because that means others having power over us, restricting both our negative and our positive freedoms), and they have some justifiably sharp things to say about Rawls' late advocacy of a static economy. For some people's taste Schimdtz and Brennan will seem insufficiently attentive to the pockets of desperate poverty which continue to exist within market societies, though they are sensitive to the erosions of civil liberty within contemporary liberal democracy, and also to problems arising from lack of what they call psychological freedom.

For, even given that in terms of wealth and status we have the ability and means to control our own lives to some degree, positive freedom in an external sense, are we free psychologically, free internally so to speak? Maybe we are prey to all sorts of social pressures impacting on our actual choices and decisions, and maybe for many of us too much freedom is itself an intolerable and paralysing burden. Maybe we are, as they put it, shackled by the dearth of shackles. It would perhaps be unfair to criticise a history of liberty for not resolving this last issue, apart from making the obvious point that few of us would wish to return to a situation of more shackles, in which other people run our lives for us. A not insignificant quibble with Schmidtz and Brennan at this point would be to point out that for all our talk about living in a free society, for many of us others actually do run our lives, in important areas such as education, health and welfare. And here, we suspect, we touch on a deep philosophical divide, often not addressed honestly even in discussions of ‘positive’ freedom; this is the divide between those who think that individuals should be in control of their own lives to the greatest extent possible, and those who think they should not, and who, for example, would run their children's education for them (a group which includes most politicians, and, one imagines from what one reads in political philosophy and the philosophy of education, many philosophers too).

Responsibility is a notion fundamental to any serious discussion of liberty. So just what are we responsible for? On any analysis we are responsible for the intended and foreseen consequences of what we do, but as George Sher demonstrates in Who Knew? Responsibility Without Awareness (Oxford University Press, 2009), there are plenty of cases where we would hold people responsible for things they failed to foresee and did not control, but perhaps should have; or for things could not have controlled at the time of acting, but which they should have taken more care to avoid, and would have, had they been different in this respect. Sher develops an account of responsibility which goes deeper than what is in an agent's mind and under his or her control at the point of acting. For Sher aspects of our earlier character have a bearing on what we are responsible for. Thus he would hold an agent responsible for consequences of his or her actions which arose from a blameworthy failure to recognise that the action was wrong or foolish, perhaps because of attitudes, dispositions or traits which lead him or her at the time of acting to ignore or discount relevant evidence. This is surely sensible, but like the work of Schmidtz and Brennan, it takes us back beyond both discussions to the deeper metaphysical question as to how far unchosen and possibly unalterable aspects of our character and psychology circumscribe our liberty.