I am always struck by how few students challenge the underlying ethics of the idea that we ought to save the lives of strangers when we can do so at relatively little cost to ourselves. At the end of the nineteenth century WH Lecky wrote of human concern as an expanding circle which begins with the individual, then embraces the family and 'soon the circle... includes first a class, then a nation, then a coalition of nations, then all humanity, and finally, its influence is felt in the dealings of man [sic] with the animal world'.1 On this basis the overwhelming majority of my students seem to be already in the penultimate stage – at least – of Lecky's expanding circle. There is, of course, for many students and for various reasons a gap between acknowledging what we ought to do, and doing it; but I shall come back to that issue shortly.

Our century is the first in which it has been possible to speak of global responsibility and a global community. For most of human history we could affect the people in our village, or perhaps in a large city, but even a powerful king could not conquer far beyond the borders of his kingdom. When Hadrian ruled the Roman Empire, his realm covered most of the 'known' world, but today when I board a jet in London leaving what used to be one of the far-flung outposts of the Roman Empire, I pass over its opposite boundary before I am even halfway to Singapore, let alone to my home in Australia. Moreover no matter what the extent of the empire, the time required for communications and transport meant that there was simply no way in which people could make any difference to the victims of floods, wars, or massacres taking place on the other side of the globe. By the time anyone had heard of the events and responded, the victims were dead or had survived without assistance. 'Charity begins at home' made sense, because it was only 'at home' – or at least in your own town – that you could be confident that your charity would make any difference.

Instant communications and jet transport have changed all that. A television audience of two billion people can now watch hungry children beg for food in an area struck by famine, or they can see refugees streaming across the border in search of a safe place away from those they fear will kill them. Most of that huge audience also have the means to help people they are seeing on their screens. Each one of us can pull out a credit card and phone in a donation to an aid organization which can, in a few days, fly in people who can begin distributing food and medical supplies. Collectively, it is also within the capacity of the United Nations – with the support of major powers – to put troops on the ground to protect those who are in danger of becoming victims of genocide.