It was a conspiracy theorist's dream. Last year, after decades of official denials, the US government finally convened a panel of NasaThe National Aeronautics and Space Administration, responsible for the US space programme. scientists to report on the existence of UFOsUnidentified Flying Objects.

That panel reported their findings this week. But it turns out they have more questions than answers.

They examined around 800 reports of UFOs - or what they now call "unidentified anomalous phenomena", UAPs. 

Most of them could easily be explained. One object that a military pilot was "convinced" must be a UAP turned out to be a Bart Simpson balloon.

But the researchers said they could not find explanations for between 2 and 5% of reported sightings. That suggests there is still a mystery to be unravelled.

Nasa cautions against assuming that these unexplained sightings must be of extraterrestrial origin. They say it is much more likely they come from other states on Earth.

But some reports are truly baffling. They describe objects that move in ways nothing on Earth can, that can climb to 30,000 feet and reach hypersonic speeds despite having no detectable propulsion system.¹

That is why some think it is worth preparing for the likelihood that we will make contact with aliens in the near future. And for philosophers, this raises many interesting questions.

In the 17th Century, as we began to make observations of other planets, most philosophers assumed that these worlds, like Earth, must have their own forms of life.

However, since they were mostly Christians, this posed difficult questions. Had the sacrifice of Christ on Earth also redeemedTo save something from bad things or faults. the inhabitants of these other planets? Or would they have needed their own savioursSomeone who saves something or someone from danger. In a religious context, it is often souls being saved.?

Today, the existence of aliens raises other profound issues. Some argue that if we are the only sentientAble to perceive or feel things. species to exist then we might have a moral duty to populate other worlds. 

This is because humans would then be the only beings in the universe capable of creating meaning. If we succeed, we fill the universe with consciousness. If we fail, it goes back to being empty and meaningless.

On the other hand, some argue, if we come across non-sentient life on other planets, we will have to decide whether to treat them in the same way as animals on Earth, or give them a complete new set of rights. 

And, they say, it might not be justifiable for us to colonise their planets just to fill the universe with meaning. In the future, that non-sentient life might have evolved sentience. By taking over their planet we would be denying them that chance.

Finding sentient life in the universe would only give us more moral problems, others say. While moral codes differ across the world, every human society has the same basic rules: no killing, no stealing, no torturing.

But aliens might have a completely unrecognisable understanding of morality. This would force us to question our own deep-held moral beliefs. And we would have to work out if we should behave towards them according to their moral codes, or our own.

Yes: Philosophers have always thought the existence of aliens is likely. Some have even dedicated their lives to working out the logical questions that they would raise.

No: Aliens give philosophers all kinds of fun and interesting thought experiments. But in the end the question of whether or not they actually exist is not a philosophical question, but a scientific one.

Or... If aliens do exist, then much of what we know about philosophy will be turned on its head. So one important question is: if aliens exist, can we continue to be philosophers?