Like former persons, future persons, the individual members of future human generations, are, from our present temporal vantage point, nonexistent. They are not alive, not sentient, and are not agents in the usual sense because they cannot act in the present. But, like former persons, actual future persons, those human persons who will one day exist, form links in the great chain of begetting that from the evolutionary perspective stretches back in time to our ancient hominid ancestors, and before that, to those life forms that preceded them in the Earth's tree of life. We would like to believe that at least some actual future persons will exist, but we cannot know for sure.
It is curious, then, that we do not also construct monuments for future persons. Monuments to future persons would serve to symbolize our connection to those who will come after us, and who will inherit the kind of intrinsic moral value we presently have. Perhaps it would be a good thing if we invented this practice in order to remind ourselves that future generations of human beings, those human persons who are "yet to be", are also in some sense "with us now" as the future heirs to our civilization and to the particular kind of intrinsic moral value that human beings possess.
It is really even more important that we remind ourselves of our relationship to future people because, unlike the dead, future persons can be harmed by our present actions.
Future persons are vulnerable to us, but we are not vulnerable to them.
Joel Feinberg dreamt up a case that illustrates this rather strange asymmetrical relationship of vulnerability. Suppose, the story goes, Sam has the malevolent intention to commit the perfect crime. He decides that one way to do this is to construct a powerful bomb that is on a very long-delay timer and bury it deep underground. He constructs such a bomb and sets its timer to detonate in fifty years. Suppose that Sam dies 32 years before the bomb explodes. After his death an elementary school is built on the site over which Sam's bomb has been buried. Thirty-two years after Sam dies, the bomb explodes, and kills scores of innocent children, children who had not even been born when Sam constructed and armed the bomb and who Sam did not know would be harmed by his actions.
There is a straightforward sense in which is seems correct to say that Sam harmed those children, even though Sam was not alive at the time they were harmed, he was a former person. There is also a strong moral intuition that what Sam did was seriously morally wrong; it was in fact a crime. Forensic and police investigations might be able to determine that it was Sam who committed this crime, and to hold him responsible, in the liability sense, for this action. But as a deceased or former person Sam is beyond the reach of the law; Sam cannot be punished for his crime, since Sam is already dead and is, at the time the bomb explodes, therefore invulnerable. Sam, it appears, got away with the perfect crime.
Yet, despite this, our moral judgment about the wrongfulness of what Sam did seems secure. At the time he set the bomb to explode in fifty years Sam had a moral responsibility not to harm any future persons. He violated this responsibiliity even though he may not have known that an elementary school would be built over the site where he buried the bomb, and he did not know, in particular, which actual future children he would be harming when the bomb exploded. Sam acted recklessly with regard to the well-being of future persons who could be harmed by his actions, and so Sam committed a moral wrong. If future persons discover by forensic investigation that it was indeed Sam who set the bomb that killed the school children, they might assign to him the status function "murderer" because Sam was the moral agent who recklessly caused the children to be killed. That Sam constructed this bomb and set it to go off in fifty year is part of the causal chain leading to the children's deaths. It is a natural fact. But the status-function "murderer" is not; it is an observer-relative judgment we make in hindsight.
This story has obvious relevance to the environmental crisis of the twenty-first century. The present generation of living human beings is destroying natural ecosystems, polluting the air and the water, causing species extinctions, and warming the earth's atmosphere by continuing to pump greenhouse gases into it. We are recklessly setting bombs on long delay fuses that will one day harm future persons. We may not know which future persons will be harmed or killed by our present actions, but it is a pretty safe bet that there will be some actual future persons who we will harm. As the philosopher John Broome has noted,
Climate change will cause harm. Heat waves, storms and floods will kill many people and harm many others. Tropical diseases, which will increase their range as the climate warms, will exact their toll in human lives. Changing patterns of rainfall will lead to local shortages of food and safe drinking water. Large-scale human migrations in response to rising sea levels and other climate-induced stresses will impoverish many people. As yet, few experts have predicted specific numbers, but some statistics suggest the scale of the harm that climate change will cause. The European heat wave of 2003 is estimated to have killed 35,000 people. In 1998 floods in China adversely affected 240 million. The World Health Organization estimates that as long ago as 2000 the annual death toll from climate change had already reached more than 150,000. ["The Ethics of Climate Change." Scientific American, Vol. 298, No. 6 (June 2008): pp. 96-102.
But if this is true, then there is a good moral argument for not doing those things we are presently doing that will cause harm to future persons, and for compensating them for the harms that we are causing. The argument derives from an elementary moral principle that nearly everyone accepts, namely that, "you should not do something for your own benefit if it harms another person. Sometimes you cannot avoid harming someone, and sometimes you may do it accidentally without realizing it. But whenever you cause harm, you should normally compensate the victim." The kinds of harms likely to be brought about by global climate change are not intentional, and are the result of our collective rather than our individual actions, yet it seems that this elementary moral principle still applies.
In going about our daily lives, each of us causes greenhouse gases to be emitted. Driving a car, using electric power, buying anything whose manufacture or transport consumes energy--all those activities generate greenhouse gases that contribute to climate change. In that way, what we each do for our own benefit harms others. Perhaps at the moment we cannot help it, and in the past we did not realize we were doing it. But the elementary moral principle I mentioned tells us we should try to stop doing it and compensate the people we harm.
This same principle also tells us that what we should do about climate change is not just a matter of weighing benefits against costs--although it is partly that. Suppose you calculate that the benefit to you and your friends of partying until dawn exceeds the harm done to your neighbor by keeping her awake all night. It does not follow that you should hold your party. Similarly, think of an industrial project that brings benefits in the near future but emits greenhouse gases that will harm people decades hence. Again suppose the benefits exceed the costs. It does not follow that the project should go ahead; indeed it may be morally wrong. Those who benefit from it should not impose its costs on others who do not.
While this seems straightforward enough from a common sense moral point of view, philosophers such as Broome, Derek Parfit, Gregory Kavka, and my colleague Melinda Roberts, have found reasons to wonder about whether our ordinary sorts of moral status ascriptions can be applied to future persons. The question is: How can we, presently existing moral agents, have moral responsibilities towards future persons?
With regard to former persons, we can use what philosophers call "rigid designators" such as proper names to refer to particular individuals. For instance, the proper name "George Washington" refers to an actual former person who was the first president of the United States of America. The proper name "Hamlet" on the other hand, does not refer to any actual former person; it refers to a fictional character created by William Shakespeare (who may or may not be the actual former person who wrote the play of the same name).
But future persons cannot be referred to by proper names and other rigid designators. We can talk about the "descendants of Thomas Jefferson" and that class includes all of that dead president's past, present, and future biological descendants. But this predicate is not a rigid designator and does not pick out just one feature of the actual world, but rather features of many possible worlds.
Unlike former persons, future persons depend for their existence on our present choices and actions.The basic source of puzzlement arises when we realize that which future persons will actually exist will depend in part on our present choices and actions. So consider the fact that it is now know that Thomas Jefferson had some descendants that the fathered with his slave Sally Hemings, probably two sons named Eston and Madison Hemings. As of 2007 there are several known descendants of Eston and Madison Hemings, but the descendants of another person who claimed to be desended from Jefferson, Thomas Woodson, have had this claim conclusively disproved by DNA evidence. (See Sally Hemings' Descendants)
Whether or not someone is or is not a descendant of Thomas Jefferson is a natural fact about them. It is not just a matter of an observer relative status attribution. Had Jefferson acted differently, those descendents of his whose other ancestor was Sally Hemings would not now exist. So then, suppose that Jefferson had not procreated with Sally Hemings. His sons Eston and Madison would never have existed, nor would their descendants, and theirs, and so on down to the present living descendants of Thomas Jefferson and Sally Hemings.
But a puzzling question now presents itself: Would Jefferson have harmed Eston and Madison and all of their descendents had he chosen not to have procreated with Sally Hemings? Generally speaking, to harm someone is to make them worse off than they would otherwise have been. But, Jefferson's sons Eston and Madison would not have been at all had he not had sex with his slave Sally, so it is hard to see how his not having done that would have harmed them. Is not existing a harm? Is existing a benefit? Who is it that Jefferson would have made worse off had he not had sex with his slave?
There are deep philosophical puzzles here that some of our best philosophical minds have been struggling to understand for the past twenty-five years or so. It seems that unless we can find some way to "fix" the reference to future persons in statements like "Future persons can be the objects of our present moral responsibilities," we cannot save the commonsense moral intuitions discussed earlier that lead to the conclusion that we ought to avoid doing things now that will likely cause harm to members of future generations.
I am not here going to offer an account of future persons that solves (or dissolves) these philosophical paradoxes concerning future persons. Instead I will adopt the strategem of referring to actual future persons, where that term should be understood to mean those persons who will come into existence because of chains of procreation that have actual causal links to present human persons. It does not include all of the possible future persons, who may or may not come to exist depending on what we do and do not do, but only those persons, who, from a "God's Eye" view of time, will actually come to exist, those who, like us and our deceased ancestors, have left, are leaving, or will leave scratch marks in the causal structure of the cosmos.
It seems clear to me that within a scientific ontology that regards what is real as everything that leaves scratch marks in the causal structure of the cosmos, actual future persons can be moral patients, that is, they can function as the objects of our moral responsibilities, the sorts of things towards whom we can have moral obligations.
To illustrate this notion, suppose that the set of actual future persons is non-empty, and that it includes someone who is my great, great, great grandson, whom I will call "John Smith." (For the record, I have no male descendants, but I do have three daughters none of whom have children at the present). John Smith does not now exist, he is an actual future person, because he will be connected to me by means of my DNA being passed down through my daughters, to their children, and from them to theirs, and from them to theirs, and from them to theirs, one of whom is John Smith. I can have a moral responsibility towards John Smith which includes my refraining from doing things that would harm him when he comes into existence, for instance, by using up non-renewable resources that he will need, or by making it the case that conditions of his life are more difficult or dangerous than they would otherwise be had I not refrained from doing certain things. I could, for instance, refrain from planting a bomb on a long-delay fuse under the spot where his elementary school will one day stand.
From a "God's-eye" or tenseless perspective, John Smith is thus vulnerable to me and is depending on me not to do certain things that would make his life more difficult or more dangerous. Under the Vulnerability Principle, I have a moral responsibility to refrain from such actions. I have this responsibility towards John Smith, who functions as a moral patient and as the object of my moral responsibilities, even though I will be dead when John is alive. From John's temporal point of view, I will be a former person, one of his ancestors. He will not be in a position to punish me or demand compensation for any harm that I may have caused him, because I will be dead, and therefore, invulnerable.
But even though I will be invulnerable to John Smith, he will be vulnerable to me. This asymmetry of vulnerability is the result of the causal directionality of time: we cannot change the past, but we can change the future. There is no such thing as backward causation (despite what Broome has thought), but there is obviously such as thing as forward causation. My present choices and actions (and yours) can participate in causal chains that produce conditions in the future that will make John Smith's life more difficult and dangerous than it needs to be, given the causal structure of the cosmos.
Thus, there is also a sense in which John Smith, and all of the other actual future persons, are depending on us, to fulfill our moral responsibilities towards them. There is a kind of intergenerational interdependence in which our ancestors, former persons, depend on us to preserve what was best in their legacies, and future persons, like John Smith, depend on us to ensure that their lives are not more difficult and dangerous than they need to be.
The VP tells us that we acquire special moral responsibilities to protect the interests or "goods" of moral patients who are specially vulnerable or in some way dependent on our choices and actions. Hence it follows that we, present persons, have special moral responsibilities to protect the interests of the actual members of future human generations, whomever they turn out to be.