As a child, you tend to take your position in life for granted, as written into the natural order of things. You were born, say, into a white middle-class family, you are comfortably off, in good health and not in any particular distress. You have rights and privileges, and these are generally respected. You aren't hungry or imprisoned or enslaved. You go on nice holidays. At an early age, you probably assume everyone lives like this. It seems natural that you enjoy the kind of life providence has granted you. You don't think about it.

Then you start to notice that others are less fortunate (and some others more fortunate). You see people around you who are poorer than you, possibly homeless, or who have something serious mentally or physically wrong with them. You start hearing about people in foreign countries who are starving to death, or being blown up in wars, or suffering from terrible diseases. Some of them are children like you! These facts jar on you; and they force you to make comparisons with your own life. Soon you are struck with a certain terrifying thought: that it is really just luck that you are not in their shoes. You happen to have been born into a certain class, in a certain part of the world, with certain social arrangements, at a certain period in history. But there is nothing necessary about this — it is just the luck of the draw. Things could have been different in ways that don't bear thinking about. You ask yourself what your life would have been like if you had drawn the short straw and lived in less felicitous circumstances. You imagine yourself born into a land of famine, or arriving on the scene before medicine made any progress with plagues, or before modern plumbing. You thus entertain a kind of philosophical thought: that it is just contingent that things are as they are, and that you could have been very much worse off. You are just lucky. Equivalently, you see that it is just bad luck for the others that their lives are as hard as they are. There is no divine necessity or inner logic about any of this. It is basically a moral accident. There but for fortune . . .

And with this thought social conscience begins. Since there is no deep necessity about the ordering of well-being among people, we should try to rectify (avoidable) inequalities and misfortunes. The arbitrariness should be removed from the distribution of well-being. We should discover the sources of misery and deprivation and try, where possible, to erase them. We should certainly not voluntarily contribute to the disadvantaged position of others. We should not exploit the power that is ours by sheer cosmic luck. Thus, morality is founded in a sense of the contingency of the world, and it is powered by the ability to envisage alternatives. Imagination is central to its operations. The morally complacent person is the person who cannot conceive how things could have been different; he or she fails to appreciate the role of luck - itself a concept that relies on imagining alternatives. There is no point in seeking change if this is the way things have to be. Morality is thus based on modality: that is, on a mastery of the concepts of necessity and possibility. To be able to think morally is to be able to think modally. Specifically, it depends upon seeing other possibilities - not taking the actual as the necessary.

I think, to come to the present point, that human adults persistently underestimate the role of biological luck in assuring our dominion over the rest of nature. We are still like children who take the contingent facts to be necessary, and thus fail to understand the moral significance of what actually goes on. People really do believe, in their bones, that there is a divine necessity underwriting our power over other species, so they fail to question this exercise of power. Indeed, this assumption is explicitly written into many religions. In every possible world we are at the top of the biological tree. As children, we naively took our family position to be the locus of cosmic necessity; now we assume that our species position is cosmically guaranteed. We assume, that is, that our relation to other species is basically the way things had to be, so that there is no point in questioning the ethics of that relation. Hence social conscience stops at the boundary of the human species, give or take a bit of supererogation here and there. We don't take seriously the idea that it is just luck that our species is number one in the biological power hierarchy. So our conscience about our conduct in the biological world isn't pricked by the reflection that we might have been lower down in the scale of species domination. We therefore need to bring our species morals into line with the real facts of biological possibility.

To be specific, we fail to appreciate that we could have been in the kind of position with respect to another species that apes now occupy with respect to us; so we protect ourselves from the moral issues that arise about our actual relation to apes. Or rather, we acknowledge the contingency of our biological position in odd and localised ways - as if our unconscious recognises it only too well but we repress it in the interests of evading its moral consequences. For our instinctive species-ism wavers when we consider ourselves on the receiving end of another species' domination. We allow ourselves to enter into this contingency in certain special sealed-off imaginative contexts - not in the world of hard moral and political reality. Significantly, these contexts typically involve horror and fear and loss of control. For the most part, nowadays, they take place in the cinema. I am thinking, of course, of science fiction and horror films. Here alternatives to our biological supremacy are imaginatively explored. Let me mention three types of fiction in which we humans assume a position of species subjugation - or contrive to escape such a position against considerable odds.

First, of course, there are the invading aliens from outer space, who come to destroy or parasitise or enslave the human species - the body-snatchers, stomach-busters and mind-controllers. Here the thought is that only space protects our species from the depredations of more powerful beings, so that space travel is a potential route to species demotion. Sheer distance is the saving contingency here. It is just luck that those aliens don't live on the moon, or else we would be their playthings even now.

Then there are the vampire stories, in which the theme of using the human species for food is paramount. A colony of vampires lives off the human inhabitants of a certain area, drinking their blood, killing other humans who get in their way. The humans are just a herd for the vampires. Usually the vampires are depicted as extraordinarily evil, gloating over the soon-to-be-punctured necks of their beautiful young victims, but sometimes they are portrayed more sympathetically, as just doing what nature designed them to do - slaves to their own biology, as it were. In any case, they are perceived as a terrifying threat to humans, and there is generally a good deal of luck involved in fending them off. It was a close thing that the entire human species wasn't condemned to be vampire-feed for all eternity. And it is lucky that we, the viewers, weren't born in Transylvania.

A third category of human demotion introduces machines, our machines. I suppose Frankenstein's monster comes into this category, since it was constructed by a human, albeit from organic parts; but a more recent example of the genre is the Terminator movies, in which the international computer network controlling nuclear weapons achieves self-consciousness one day and, fearful for its own survival at human hands, begins to wage war on its human creators, with very nasty consequences. This computer constructs its own formidable robots ('terminators') whose mission is simply to kill as many humans as possible, and they will not stop. This, then, is a case in which our artifacts rise up and exert domination over us, bringing untold havoc and misery to our species. And here the contingency is merely the level of technological advancement of our machines. If we are not careful, the message goes, our technology will come back to oppress us; so we had better not rely on luck to prevent this happening in the future. In fact, if time travel is possible, we should be thinking about it now, since the future may contain the very terminating machines made possible by extensions of our present technology. So, at least, the movies suggest.

Well, this is all good entertaining fun, but the point I want to make is that these nightmare fantasies represent, in sublimated form, our repressed sense of the contingency of our biological supremacy as a species. They are saying,' You could be in the position that other species are actually in — that you put them in.' And, of course, we are supposed to sympathise with ourselves in these possible fantasy worlds: we applaud the freedom fighters who seek to liberate us from the selfish domination of other kinds of being. We certainly don't think that might is right in these battles between the species. We have to fight them precisely because they are morally blind to what they are doing to us, or just outright callous. What I am suggesting now is that we take seriously the notion that we might have been, or could be, in such a position, and ask ourselves what moral principles we would want to see observed if indeed we were the weaker species. That is, we need a species morality informed by the idea of biological luck. Equivalently, we need to ask ourselves what rights need to be granted to species who happen to be thus subservient to us — apes in the present case. How does it look from their point of view? If humans had never evolved, then there would have been no scientific experimentation using apes as subjects, no confinement of apes in zoos and elsewhere, no systematic killing of apes for sport. Apes would undoubtedly have been better off without us. They are cosmically unlucky in the way we would be if any of the above nightmares become reality. And just as we would fight to have the evil effects of such bad luck reversed in our case - using sound moral argument as our justification - so we should recognise that the bad luck of apes in having humans to contend with should not be allowed to continue unchecked. In short, we should stop oppressing them. We should accord them the rights their intrinsic nature demands, not just acquiesce in the abuses of power consequent upon our chance biological supremacy. We might have been the ones in the cages or on the vivisection tables: and it is a cast-iron certainty we would not have liked it one bit. Morality, in short, should not be dictated by luck.

Let me end with an idea for a screenplay. We are a couple of million years into the future, and time has not been kind to the human species. Human intelligence reached a plateau in the twenty-first century, when the physiological constraints of giving birth stopped infant heads getting any bigger. Unluckily, too, the diseases of the modern world -physical and psychological — were not vanquished, leaving humans a generally sickly and neurotic lot. The pollution, the overeating, the crime, the stress have made humans a weak and enervated species. However, the apes have enjoyed a steady march forward. Their frontal lobes have been expanding all the time, they are fit and robust, and they have long since thrown off their human shackles. They have all the trappings of civilisation. Now, in fact, the status quo has been reversed: humans are now vulnerable to their whims. Some of the more unscrupulous of the gorillas — the ones with the flashy houses and private jets — have gone into business selling human specimens for a variety of purposes, no questions asked. Some go for medical experiments designed to benefit apes, others to slaughterhouses, the lucky few become pets, yet others are sold for interspecies prostitution. So far this is all illegal, done on the black market, and is officially frowned upon by the apes' government. But it is easy to arrange, given the vulnerable state of so many humans. The big problem, for the ape entrepreneurs, is getting the trade in humans accepted and legalised, so that they don't have to operate on the wrong side of the law. There is this annoying ape lobby, you see, that disapproves of subjugating humans in these ways, and, of course, the humans are less than thrilled about it themselves. The shady businessapes are working on the corruption of some high officials to get them to pass a law allowing what is now only done illegally. The propaganda, thankfully, is a breeze, given what all apes know about their treatment at the hands of humans for so many centuries — it is there in the history books. Serves them right, does it not? It looks like they are going to succeed in institutionalising their exploitation of humans, unless that brave coalition of good apes and desperate humans can prevent them . . .

OK, my point is this. Suppose this story became reality: wouldn't it be better to be able to say to the apes, who are generally a kind and decent species, that we stopped exploiting them voluntarily in the last decade of the twentieth century? We saw the error of our ways, so why should they repeat our earlier mistakes? We were not simply forced, by their biological ascendancy and our decline, to grant them rights in the middle of the 1000th century, say, after a bloody war; we just did it from moral principle well before we could be made to. We could thus appeal to their moral sense by citing our own earlier moral example. We would have an answer to the more cynical apes who insisted it was just our 'bad luck' that they have now assumed the more powerful position. I, at least, would like to think that, if my screenplay comes to pass one day, our human offspring will have some moral case to make against their own ruthless exploitation at the hands and jaws of other species. If we can do it, why can't they?