Martin Rees on existential risk:

I am concerned about the threats and opportunities posed by 21st century science, and how to react to them. There are some intractable risks stemming from science, which we have to accept as the downside for our intellectual exhilaration and—even more—for its immense and ever more pervasive societal benefits. I believe there is an expectation of a 50% chance of a really severe setback to civilization by the end of the century. Some people have said that’s unduly pessimistic. But I don’t think it is: even if you just consider the nuclear threat, I think that’s a reasonable expectation.

If we look back over the cold war era, we know we escaped devastation, but at the time of the Cuba crisis, as recent reminiscences of its 40th anniversary have revealed, we were really on a hair trigger, and it was only through the responsibility and good sense of Kennedy and Khrushchev and their advisers that we avoided catastrophe. Ditto on one or two other occasions during the cold war. And that could indeed have been a catastrophe. The nuclear arsenals of the superpowers have the explosive equivalent of one of the US Air Force’s daisy cutter bombs for each inhabitant of the United States and Europe. Utter devastation would have resulted had this all gone off.

The threat obviously abated at the end of the cold war, but looking a century ahead, we can’t expect the present political assignments to stay constant. In the last century the Soviet Union appeared and disappeared, there were two world wars. Within the next hundred years, since nuclear weapons can’t be disinvented,  there’s quite a high expectation, there will be another standoff as fearsome as the cold war era, perhaps involving more participants than just two and therefore be more unstable. Even if you consider the nuclear threat alone, then there is a severe chance, perhaps a 50% chance, of some catastrophic setback to civilization.

There are other novel threats as well. Not only will technical change be faster in this century than before, but it will take place in more dimensions. Up to now, one of the fixed features over all recorded history has been human nature and human physique; human beings themselves haven’t changed, even though our environment and technology has. In this century, human beings are going to change because of genetic engineering, because of targeted drugs, perhaps even because of implants into their brain to increase our mental capacity. Much that now seems science fiction might, a century ahead, become science fact. Fundamental changes like that—plus the runaway development of biotech, possibly nanotechnology, possibly computers reaching superhuman intelligence—open up exciting prospects, but also all kinds of potential scenarios for societal disruption—even for devastation.

On the simulation argument:

One thing which struck me recently, and I found it a really disconcerting concept, was that once we accept all that, we get into a very deep set of questions about the nature of physical reality. That’s because even in our universe, and certainly in some of the others, there’d be the potential for life to develop far beyond the level it’s reached on earth today. We are probably not the culmination of evolution on earth; the time lying ahead for the earth is as long as the time it’s elapsed to get from single-celled organisms to us, and so life could spread in a post-human phase far beyond the earth. In other universes there may be an even richer potentiality for life and complexity.

Now life and complexity means information-processing power; the most complex conceivable entities may not be organic life, but some sort of hyper-computers. But once you accept that our universe, or even other universes, may allow the emergence within them of immense complexity, far beyond our human brains, far beyond the kind of computers we can conceive, perhaps almost at the level of the limits that Seth Lloyd discusses for computers—then you get a rather extraordinary conclusion. These super or hyper-computers would have the capacity to simulate not just a simple part of reality, but a large fraction of an entire universe.

And then of course the question arises: if these simulations exist in far larger numbers than the universe themselves, could we be in one of them? Could we ourselves not be part of what we think of as bedrock physical reality? Could we be ideas in the mind of some supreme being, as it were, who’s running a simulation? Indeed, if the simulations outnumber the universes, as they would if one universe contained many computers making many simulations, then the likelihood is that we are ‘artificial life’ in this sense. This concept opens up the possibility of a new kind of ‘virtual time travel’, because the advanced beings creating the simulation can, in effect, rerun the past. It’s not a time-loop in a traditional sense: it’s a reconstruction of the past, allowing advanced beings to explore their history.

On the direction of science:

At the moment, scientific effort is deployed sub optimally. This seems so whether we judge in purely intellectual terms, or take account of likely benefit to human welfare. Some subjects have had the ‘inside track’ and gained disproportionate resources. Others, such as environmental researches, renewable energy sources, biodiversity studies and so forth, deserve more effort. Within medical research the focus is disproportionately on cancer and cardiovascular studies, the ailments that loom largest in prosperous countries, rather than on the infections endemic in the tropics. Choices on how science is applied shouldn’t be made just by scientists. That’s why everyone needs a ‘feel’ for science and a realistic attitude to risk — otherwise public debate won’t get beyond sloganising. Jo Rotblat favoured a ‘Hippocratic’ Oath’ whereby scientists would pledge themselves to use their talents to human benefit. Whether or not such an oath would have substance, scientists surely have a special responsibility. It’s their ideas that form the basis of new technology.

On posthumanism:

Human-induced changes are occurring with runaway speed. It’s hard to predict a mere century from now, because what will happen depends on us — this is the first century where humans can collectively transform, or even ravage, the entire biosphere. Humanity will soon itself be malleable, to an extent that’s qualitatively new in the history of our species. New drugs (and perhaps even implants into our brains) could change human character; the cyberworld has potential that is both exhilarating and frightening. We can’t confidently guess lifestyles, attitudes, social structures, or population sizes a century hence. Indeed, it’s not even clear for how long our descendants would remain distinctively ‘human’. Darwin himself noted that “not one living species will transmit its unaltered likeness to a distant futurity”. Our own species will surely change and diversify faster than any predecessor —— via human-induced modifications (whether intelligently-controlled or unintended), not by natural selection alone. Just how fast this could happen is disputed by experts, but the post-human era may be only centuries away.