1. 

I remember the first time I read an article accusing me and my colleagues of being puppets of a foreign government. In that same month my sister forwarded me a video in which a preacher confirmed that I was the antichrist. And then about a week later a woman asked me to bless her child. A lot of people had a lot of ideas about what we were, but personally, I think we were just lucky. Honestly I’m surprised that nobody got there before us. But for whatever reason, I have the strange honour of being the first person in history to witness a human soul. 

I'm sure you've heard a version of this story, but let me tell it again, because I don't think you'll have heard the ending. It was autumn, in a lab in Manchester. We were working on a very speculative research project to detect microorganisms by creating these electromagnetic fields that somehow bounced off them. Honestly I still don't fully understand what it was meant to do: my job was to take the raw data and convert it into something intelligible. But I was there in the lab when it happened. 

We had the rig set up, a set of dishes and this radar gun hooked up to a speaker that would beep like a Geiger counter. Or at least that was the theory: we hadn't actually got any results yet. Lots of people tell this story like we were hard at work, all very serious in our lab coats, but the truth is that when it happened we were just playing around with the settings, cycling through different frequencies trying to get a response. 

Emily was holding the radar gun over the dishes each in turn while I was combing through the data on my laptop looking for a signal, when Jack came through the door with a tray of coffees. Emily spun around, still holding the gun, pointed it at Jack, and the speaker just blew. 

Well, we were all a little alarmed to say the least. The first thing we did was make sure the whole machine wasn't bust, but looking at the logs we saw that just before it broke,

the readings had jumped. It wasn't like they curved up, no, they went straight from dead zero to off the scales. 

We turned down the output as much as we could before we connected another speaker, pointed it at Jack again, and gradually turned it back up until once more we got a clear and recognisable signal. And we got the same signal when we pointed it at Emily, and at me. Nothing else in the room got any response. That was when we started to get curious. 

Whatever we were detecting had no trouble passing through air, but it was blocked by about a centimetre of solid matter. The only thing that triggered it was us, nothing else. And any part of our bodies would trigger it, even a dense clump of hair. After we worked that out I remember Emily said she wasn't sure why it wasn't getting any background readings from all the dust and skin everywhere. Then Jack suggested we try giving someone a haircut. 

We argued for a while about whose hair we should cut off. Back then I was growing out a ponytail, which I at least was quite fond of - there are pictures on the internet, if you're curious - but after enough coercion I decided I could sacrifice a few strands to scientific progress. So we lined up a clump of it, still attached to my head, and pointed the detector at it, with all the normal beeps, then Jack snipped it with a pair of scissors, and in that instant it dropped to nothing. That was when we knew we were on to something. 

The next few days were a blur of discovery. We brought in a select few trusted friends and reached out to some senior academics. We set to work improving the machine, salvaging parts from various other projects and departments, and eventually managed to assemble a 50x50 grid of sensors. I did the thing I am now famous for, which was in fact basically trivial: I wrote a piece of software that took the results of the sensors and converted them into an extremely low-resolution video feed. And when we turned the machine on, what the video showed was the rough shape of whatever people it was pointed at, nothing more and nothing less. There we were, co-conspirators on the frontier of scientific progress, not even slightly sure what it was we were looking at, but increasingly certain that it wasn't like anything we'd ever come across before. 

2. 

I've heard astronauts talk about the way it feels to look down at Earth, every country, every life, and cover it with your thumb. I still don't know if there's a god, or gods, or whatever, and I’ve often wondered if it was a mistake that the word we picked for what we saw was 'soul'. But what a relief! What a relief to know at last that there was something about us, something different. 

I consider it a little unfair how much credit I and my colleagues got, because all the real work came elsewhere. This is the point where my story stops, but I was fortunate enough to get a front row seat to the torrent of discoveries that followed. A team at MIT found a way of scaling our design to produce a detector for about £20. Then there was this genius grad student in Switzerland who refined our process and worked out that you can tell just from looking at a soul how much it's suffering - which, by the way, is not the same thing as experiencing pain. Whole departments got established to try to work out what the process was that caused an embryo to go from being inert to having a recognisable soul over the course of nine months, and within two years, we knew. As for animals, well, it was just a matter of tracking them down and checking. 

Dogs have souls. Not as much as us, but about 1/3, depending on the breed. Cats don't though, not even a trace. Monkeys are anywhere from 50 to 90%. Elephants actually have more soul than we do. Pigs and cows, they suffer. It's about 10%, but it's there. That one was brutal for me. I tried veganism in college and gave up because I just didn't have the energy. And then I saw a live feed of the scale of suffering in a factory farm. I'd previously tried pricking my thumb under a sensor and, if that was like a candle, this was like staring into the sun: blinding. I had to go to the bathroom and throw up. Battery chicken farming, though, seems to be fine. And plants and trees don't really have a soul. On the other hand, really big mushrooms really really do, but oddly they don't seem to suffer. 

Anyway, people were hesitant at first, as they always are with a new discovery. You don't want to upend your whole moral code and turn over millennia of tradition just because some geek in a lab coat found a way to make something beep. But once we knew what we were looking for, suddenly neuroscientists started making discoveries in leaps and bounds. Consciousness, perception, identity, they all began falling into place. Oh, the nihilists tried to stay disaffected and cynical, but it was hard to argue with the data. 

And every time somebody said something like "what if there's another kind of suffering, one your precious machine can't detect", well, a year later somebody else would publish a paper finally giving a full theoretical underpinning of what suffering actually is, and everybody who could understand it (in this case it involved quite a lot of topology) would agree that, yes, it was pretty ironclad. I'd never seen anything like it: it's as if we opened the floodgates on truth. 

Obviously reducing suffering isn't the only thing that matters, but at last it stopped being theoretical. We knew what we were doing, we knew how we were causing harm, and we stopped. The public went out on the streets, and one by one we closed the abattoirs, cleared out the cattle pens, half-emptied the zoos: there was no hiding the truth anymore. 

People often ask me if I’m proud of my discovery and honestly I’m not, but I am truly proud of the part I played in what we did next. Those of you who helped, you should be too. As for the rest of it, the chickens, the mice, the insects, and the fish, well, it took a little while to be sure and to really accept it, and of course there were other complications in every case, but we finally stopped worrying about hurting them. Because at last we knew.

I say that, but there are still a few mysteries: Cephalopods definitely have souls. The detectors can't pierce solids but, thanks to a team in Berlin, they can go through water. And if you find a big ocean trench and point downwards, well, there's something going on down there. 

3. 

I worry sometimes about the things that we don't know though. The truth ruined a lot of lives: farmers who earned their keep selling beef found the demand suddenly dropped. And, less pragmatically, some of them had to live with the knowledge of what they'd been doing. We all did, really. 

I remember in the span of days where we were trying to decide how to share our first discovery with the wider scientific community, and the press, Jack took me aside once and asked me, "What happens if not everyone has a soul?" I couldn't sleep that night. I lay in bed looking at my girlfriend and wondering, what would I do if I pointed the device at her and for the first time it stayed silent? 

But we still went ahead with the announcements. I think that even if some people hadn't registered on the machine, it's not as if we would have started harvesting them for organs, but I also think that on the whole, you have to follow the truth wherever it takes you. Even if it scares you, and even if it hurts. I'm glad it didn't come to that though. 

These days a lot of conscientious teens say that, if they'd been born 40 years ago, they'd have had the intellectual humility not to eat beef or go see monkeys in the zoo. It's hard to explain to them that back then we just didn't know how to measure the difference between a cow and a chicken, or at least, not like we can now. Or maybe I'm just making excuses.

I think they're right to talk about intellectual humility though. There's a question of compassion, whether we have the right to subject animals to extremely painful situations, and then there's a separate question, which is, how confident are we in our estimation of their capacity to suffer? I remember back then, I tried not to think about chickens in cages, but when I did I just assumed it wasn't really affecting them the way it would affect, well, a person in a cage. And in that case I was right. I just wish I'd also been right about all the beef. 

The discoveries we've made have pretty conclusively settled the issue, but they've also revealed that back then we did have more or less all the pieces, even if we didn't know how to put them together. In retrospect, the fact that we hadn't found a near-infallible proof of their suffering seems to be a poor justification for our general willingness to ignore it. There are two things I can say with certainty: I'm glad we know now, and I only wish we'd known sooner. 

But you’ve heard all this before. Why am I up here telling you all over again? The reason is simple. Once more, we as a society are going to be confronted with the answer to one of the fundamental questions of life, and once more, we must decide what to do with the answer. Once more, we will be acting under great uncertainty, and once more, perhaps more so than ever, it is vital that we remain humble in our quest to make sense of our place in the universe. Because there is more. 

A few months ago, I was informed that a research team had developed a way to reduce the interference on our readings in a vacuum to essentially zero. They put a detector on a satellite, and they've spent the past few weeks scanning the observable universe. Three days ago they found something, coming from a planet called Kepler-1652b. I'm honoured to be the one to tell you: somewhere out in space, there is another soul.