Some want to scrap the term completely. Others want to reclaim it. Some think it impossible to detach the idea of the sacred from religion, while others feel it is essential to do so. What has emerged clearly is a need among humanist thinkers to find a common language to express our moral and emotional responses and instinctive qualities that are too often suppressed in the quest for rationalism.

Clearly, the word 'sacred' has been traditionally inseparable from religious belief. A sacred building is one dedicated to the worship of a deity. A sacred text is one that is thought to have a unique kind of authority because it is a communication from a deity. But some of us believe that the word can also be used to identify a distinctive kind of emotional experience without implying any context of religious belief. Regardless of their divergent views of how this elevated, almost mystical emotional state should be described, all of the conference's contributors associate it with responses to three fundamental phenomena; works of art, the natural world, and human life itself.

"I don't think they come much more anti-religious than I do," claims Richard Dawkins. "And yet there are objects and occasions which invoke in me a profound sense of the sacred." He goes on to describe being moved to tears in the presence of the great fossils of palaeo-anthropology in Kenya or of "the strata of geological time laid out before you" at the Grand Canyon.

"The human mind is big enough, and imaginative enough, to be poetically moved by the whole sweep of geological ages represented by the rocks that you are standing among. That's why you feel awe. That's why you feel as though you are undergoing a religious experience."

Dawkins' feeling of 'awe' is echoed by Simon Blackburn. "Despite being an atheist, I find a lot of things arouse a sense of the sacred in me. Works of art or music, sublime grand spectacles in nature, the starry heavens above and the moral law within, the oldest human skulls in Kenya or the newest human baby in a maternity ward can all be fitting objects of different kinds of awe and reverence."

Blackburn's application of the word 'sublime' to both nature and art is echoed in my my own essay, where I suggest that 'sublime' is more appropriate than 'sacred' for both because our response to both natural phenomena and works of art is essentially an aesthetic one - a reaction not merely to beauty but to a wealth of expressive values.

The word 'sublime' was used by the philosopher Immanuel Kant to describe a quality, different from the quality of beauty, to which we respond aesthetically and which we find in both nature and art.

We may, for example, find storms and volcanoes terrifying, he says, but by viewing them aesthetically we can take delight in our ability to rise above that fear. I don't think that the word 'sublime' can do all the work, any more than the word 'sacred' can, but I think he's right that our feelings of awe in response to nature are in some ways like our responses to great works of art, and in both cases one of the reasons why we're moved by them is that features of the natural world and works of art are expressive of a range of human emotions. The bleakness of a barren wilderness, the awesome majesty of a mountain peak, the starkness of the cliffs, the relentless power of the crashing waves - their value consists precisely in their bleakness, their awesome character, their starkness, their relentless power.

Nigel Warburton, who would like to jettison the word 'sacred' altogether, feels it is particularly wrong to use it about art. Works of art are valuable not in themselves but only because of the kinds of responses they evoke. Suppose that a painting by a great artist - a Vermeer, say - is locked in a vault with a device which will destroy the painting if anyone tries to open it. This means that there is no possibility that anyone will ever experience the painting. In such circumstances, says Warburton, the painting no longer has value, since it can never be experienced by anyone. If we are inclined to suppose that the painting might still have value, that's only because we're cheating - imagining that there's maybe just a tiny chance that someone will somehow in the future find a way of looking at the painting. But that's to concede that what really has value is the experience of looking at the painting, not the painting itself. According to Warburton that's another reason for desisting from thinking of works of art as sacred.

Matthew Kieran takes the opposite view. Works of art do not derive their value from the experiences they afford us. Rather, we value our experiencing of them because they have qualities which evoke our admiration and sometimes our awe. What's more, says Kieran, there's a special kind of experience we can get from a work which is an original - a work by a great artist, rather than a copy - because it embodies a unique creative achievement. Original works of art are not substitutable. This is why "the destruction of works can be a desecration," and it is why works of art "can be, in a humanistic sense, as close as one can get" to the sacred.

Alan Holland appropriates Kieran's view of art as an "unrepeatable generative achievement", claiming that it applies equally to nature. We should think of nature, he suggests, not in the abstract, not as a repeatable instantiation of universal scientific laws, but as this particular natural world containing these particular natural species - "a unique and historically contingent biosphere delivered to us largely through the processes of natural selection". He argues that regarding nature as sacred for this reason "gets something right about our relationship to the natural world."

Holland's approach to this idea also helps to illuminate notions of the sacredness of human life. If what is important is the unique and irreplaceable character of each individual human life, then we have a rationale for using the word 'sacred' without any of the religious connotations of life as a gift of God or anything of that sort. Simona Giordano and John Harris, in their essay, stress that if anything is sacred it is not 'life' in the abstract but individual human lives.

But even if we do accept that human lives have a special 'sacred' value, argues Suzanne Uniacke, it doesn't necessarily follow that it can never be morally right to kill another human being. For example, "the moral permissibility of self-defence need not imply that an unjust attacker's life is not valuable, nor even that is less valuable than the life of the person who is being attacked." So the question of whether someone's life is valuable, and the question of whether it could be right to kill that person, are two distinct questions.

In this context Uniacke criticises the link made by some other contributors between the idea of the 'sacred' and the idea of being 'inviolable'. Since she thinks that killing another human being may sometimes be morally permissible, she concludes that though life may be 'sacred' it cannot be 'inviolable'.

I agree with her (as most people would) that there can't be an absolute moral prohibition on the taking of human life. As well as cases of self-defence, there may also be exceptional circumstances where killing may be the only way of preventing a terrible catastrophe or resisting an intolerable evil. Even so, I think that linking the idea of the 'sacred' with that of the 'inviolable' may be useful. It serves to mark out a special kind of value and a special kind of moral significance. Talk of 'inviolability' registers the recognition that the lives of other people set moral boundaries, limits or constraints on our actions - human lives can't simply be computed in terms of consequences, nor used as a means to an end, however worthy the goal.

This is the point that Ben Rogers stresses when he says that "value is not a single, homogeneous thing" - that some things have an "unconditional value" such that they can't simply be traded off against other goods in some overall cost-benefit analysis. In struggling to express this sense of unconditional values, secular philosophers will use words like 'sacred' or 'sacrosanct' because "these quasi-religious concepts offer them another powerful way to articulate this fundamental distinction between different forms of worth."

I have sometimes detected on the part of fellow humanists an attitude to language which verges on the superstitious. It is as though they feel that they have to avoid certain words for fear of being contaminated by their religious associations. Some even feel a bit awkward wishing each other 'Happy Christmas!'.

I want to suggest that we should be more pragmatic in our attitude to language and accept that some words can be rescued from their religious connotations, while others cannot. Often their import and associations will depend on whom we're addressing, and in what context.

What's important is that we look for a language which does justice to the richness of human emotional and moral experience. Religious believers sometimes accuse us of having a superficial and impoverished view of the world. I hope that the deliberations at the conference and in the pages of the resulting book Is Nothing Sacred? at least show that accusation to be unfounded.