Future Generations

 

In recent years the search for exoplanets has turned up a wealth of exciting results. The TRAPPIST project discovered a system of planets orbiting a dim red star, which with the help of the Spitzer Space Telescope, ultimately revealed seven Earth-sized planets. Three of the seven are located in the star's "habitable zone"--the region around the star in which we could reasonably expect liquid water to exist on the surface of the planets. Future scientific investigation of these planets aims to detect the signatures of atmospheric chemistry relevant to the conditions for life on these alien worlds. 

Why do we care if there is, or could be, life on other planets besides our own? Brute scientific curiosity, surely. But are there other reasons? In a 1997 Scientific American article "The Search for Extraterrestrial Intelligence", Carl Sagan and Frank Drake (of the Drake equation), posed a question that I have heard echoed in other contexts: "Is mankind alone in the universe?" The sentiment behind this question seems to be an important driver of exoplanet research--some humans are curious if there are other beings with whom we might meaningfully communicate outside of our home planet. (I have to admit I've found this question a bit puzzling. I mean, why not work on communicating with the dolphins and gorillas we already know about?)

Yet another reason motivating the search for habitable exoplanets is clearly the desire to populate them with human inhabitants. Think of Elon Musk's SpaceX project aimed at sending humans to Mars. But why? I wonder if a significant motivating factor is concern about the continuation of our species--about ensuring that our future generations have habitable conditions. Entertaining far-future speculation momentarily: suppose life has a billion years left on planet Earth before water on the surface of our planet boils away. If space-faring Earthlings of some sort or another survive that long, could they escape to a more hospitable part of the universe? Maybe Mars is a baby-step on the way to a much longer journey out of our solar system?

The motivation for interstellar migration raises a more fundamental philosophical question: would it be a bad thing if in the future there were no people? Suppose that a few million years from today there are no living descendants of Homo sapiens. Would that be bad? 

Often when we think of something being bad, we think of it as being bad for somebody. If I steal your bicycle that's bad for you. If I stub my toe trying to steal your bicycle that's bad for me (although I probably deserved it). But this creates a strange problem for the question about the existence of future generations. Suppose no people exist 5 million years from now. Who would that be bad for? 

Could it be bad for the non-existent future generations that could have existed, but as a matter of fact will not? It seems counter-intuitive at the very least to say that something can be bad for someone who does not and will never exist. If I never have a pet llama, even if it is possible for me to adopt a llama (although I never do), it seems nonsensical to chastise me for failing to feed my llama. It's not bad for the llama that I fail to feed it, because there is no llama to feed!

But maybe this reasoning is too fast. In "Energy Policy and the Further Future" Derek Parfit raises what he calls "a difficult question", namely: "whether causing to exist can benefit" (2010, 114). If causing a person to exist can benefit that person, then we do good by those people whom we cause to exist. Perhaps this isn't so far fetched--we may express gratitude to our biological parents for bringing us into the world. 

Consider a related question: whether failing to cause to exist can harm. This seems less plausible. I do not currently have any children. Have I thereby harmed all of the possible children I could have already had? Those very children never existed and will never exist--how could I have harmed them? So perhaps in failing to cause a (possible) person to exist, we neither harm nor benefit that (non-existent) person. But if this is so, then the implication seems to be that we do no harm to future (possible) generations by failing to cause them to exist. Remember that film Children of Men? Infertility pervades the species and humanity faces extinction. For whom would that be bad?

If not the non-existent future generations, perhaps the extinction of the human species would be bad for those of us who are now living. Humans have hopes and aspirations, some of which aim beyond the limits of their own finite life spans. Perhaps it is bad for those of us who have aspirations about the far future if those aspirations will fail. Yet, even if I would personally be saddened, and thereby somewhat harmed, to think that there will be a time when there are no more people, and that our projects as such will die with them, am I right to be thus saddened? I mean, is it really reasonable for me to personally have any stake in the very far future after I am long dead?

Suppose that the demise of humanity is neither bad for the non-existent future generations that could have been, nor bad for extant persons--is there another option? Perhaps the intuition is that it would somehow be bad for the universe--that missing humanity, the universe would be somehow lacking and thereby harmed. Familiar as this intuition is, I find it difficult to articulate justification for it. But I'm sure that difficulty is tied up in my stance regarding what the universe is. I am operating under the assumption that the universe is not itself a person, although there are certainly those who would disagree with me about that (cf. Robin Wall Kimmerer's excellent book Braiding Sweetgrass). Until we discover extraterrestrial persons, it would also be mere speculation to say that humanity's demise would be bad for them either. So would it really be bad?

If far-future generations of human beings fail to exist and this is not bad, one might wonder what all the fuss is over global climate change. Climate science experts predict that unchecked climate change will lead to an uninhabitable Earth. Under high-emissions scenarios for the future, the average global temperature could rise to more the 4 degrees Celsius above pre-industrial averages. Here's the part of Figure SPM.6 dealing with surface temperature from the most recent Assessment Report from the IPCC. You can read accessible explanations of what "RCP 8.5" means in this Carbon Brief Explainer and this article from The Atlantic. 

Suppose global climate change poses an existential threat--so what? If the reasoning I've outlined above applies, it may seem that there's nothing really bad about this. 

Of course, what is obviously distressing about climate change is the harms that it has caused, is causing, and will cause to people (not to mention other beings) who are currently alive. But what about future generations?

Parfit argues that the decisions we make now about key economic policies will impact which particular people come to exist in the future. That is, which emission scenarios and which adaptation policies we adopt will influence the causal course of events in ways that determine which humans are conceived, born, and grow up. Suppose the United States goes largely net carbon zero by 2050. That will affect what jobs people have, where they live, how they get around, and plausibly who they make babies with and when. If you have children in the future, who precisely those children will be will likely turn out to be different depending on what climate policies we adopt now. Parfit argues that insofar as we decide to adopt climate policies that will be harmful for future generations (whoever they happen to be), we can not technically say that our decisions would harm those future persons because, he argues, but for those very decisions those particular persons would never have existed. To see this, imagine a person who will exist in the far future attempting to curse us for making overly selfish decisions about climate policies: "I would curse you for your selfishness, except if you had chosen otherwise than you in fact did I would never have been born!" Yet, Parfit argues that this technicality makes no moral difference and that perhaps we even ought to ignore the issue when we discuss climate decisions and their moral ramifications in public (2010, 118).

So even if Parfit is right that technically speaking short-sighted climate policies do not harm the very persons that will come to exist in the future, future persons (disregarding their particular identities) will be worse off with those short-sighted policies then future persons (disregarding their particular identities) would have been if we chose better policies. 

Do we harm the persons who will never come to exist as a result of our climate policy decisions? Insofar as I do no harm to the (non-existent) children I could have had so far but didn't, it seems to me that we do no harm to those possible persons that would exist if we chose short-sighted climate policies but will fail to exist in particular, if we choose better policies. If there will be future humans at all, we should aim to set them up to flourish, regardless of which persons in particular they will happen to be.