In Cixin Liu’s acclaimed “Three Body Problem” trilogy all civilisations in the Universe are conceived as living in a “Dark Forest”. In this dog-eat-dog, or alien-exterminates-alien, vision, all cower in the blackness terrified of even being detected by each other, and always attempting to eliminate their rivals if they do. In this seemingly never-ending genocidal war of all against all, ferocious weapons have been developed that bend the laws of physics itself.

In particular, species attempt to literally crush their rivals by reducing the dimensions of their space. Step by grim step, a once spectacular n-dimensional Universe has been collapsed down to our mundane three dimensions by the expanding side-effects of these devices. Now weapons have been used that are rapidly reducing even our own meagre three dimensions down to two.

Is there a way to avoid the cold, ruthless, logic of the Dark Forest? In a reality where humans, a single species, and one that is among the top 5% of the most genetically uniform primates, are often lethally vile to each other, murdering and exploiting on scales from the individual to the tens of millions, like an army of evil but mutually loathing clones, could sentient beings with no shared origins ever find a way to live together?

Is there, in short, a universal morality?

Focussing down further on this question, what would it mean for a morality to be “universal” in the first place? We are going to assume that, in this context, “universal” means a morality capable of, at least conceivably, being freely and knowingly accepted by any being with any capacity to understand it. After all, would we accept a morality as universal if it didn’t have those characteristics?

By contrast, a non-universal morality means mere moral relativism, and then inevitably descending back into the Dark Forest, as then there are no principles regulating how participants in the different “moral relativisms” should behave towards each other. Therefore, if we seek a general or ultimate morality at all, no other form of morality is even possible. The only fundamental morality that can be proposed at all is one that could apply to all beings: a “universal” morality as just described.

Note that this morality isn’t god-given, for these beings won’t share the same gods, or any gods, nor is it something evolved, or hard-wired, and inherent, because these beings may not share the same origins. Rather, a universal morality has to be derived from reason alone, in the same way as a proof in game theory.

So what is this universal morality?

In a way, we are likely to know the answer already.

What is “moral” is to respect the wants and needs of others as equal to your own, provided they reciprocate, i.e., to not be needlessly selfish.

Otherwise we have to posit entities that would knowingly and freely submit to a system of morality that would not accord their deepest wants and needs, meaning whatever it is they hold most dear, the same respect as the wants and needs of other adherents of the same system of morality. That involves those beings having to act “freely” but also in a way that does not follow from their own motivations, which is internally contradictory.

As implied, respecting the wants and needs of others as equal to your own, provided they return the favour, may sound familiar. As humans have come to live together in ever larger groups, it is roughly the morality that we have hit upon semi-accidentally many times before. It is very close to the Golden Rule, with an extra emphasis on reciprocation, associated with many mainstream religions and forms of humanism.

For example, it is equivalent to the principle of “We must treat others as we wish others to treat us”, adopted as a “Global Ethic” by the Parliament of the World’s Religions, or the “treat others as you treat yourself” of the first millennium BCE Mahabharata. That’s because, in the final analysis, the “treatment” we expect of others is to respect our wants and needs as much as their own.

It shares with the Categorical Imperative, “act as if you are a universal legislator”, of the philosopher Immanuel Kant, as it encourages us to act as we want others to act, rather than acting in a way that advances our own interests but at the expense of others.

It shares with Utilitarianism the principle of equivalence of the well being of all. In other words, that I can not value my own well being higher than that of others, though with a stronger impetus towards equality rather than merely maximising total Utility.

In these times of “polycrisis” we need to rebuild our variously failing social systems from the bottom up. We need a strong moral foundation to do that. We must re-discover this universal morality, as otherwise it is the “Dark Forest”, in some form or other, for all of us.