The Saturation View

A new theory of population ethics

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In collaboration with Christian Tarsney, I’ve developed a new theory of population ethics, which I call the Saturation View. I think that, from a purely intellectual perspective, it’s probably the best idea I’ve ever had. It was certainly great fun to work on.

The motivation is that many views of population ethics, like the total view, suffer from some major problems. Some are already widely discussed:

• The Repugnant Conclusion: For any utopian outcome, there’s always another outcome containing an enormous number of barely-positive lives that is better.

• Fanaticism: For any guaranteed utopian outcome, there’s always some gamble with a vanishingly small probability of an even better outcome that has higher expected value.

• Infinitarian Paralysis: Given that the universe contains an infinite number of both positive and negative lives, no finite or infinite change to the world makes any difference to overall value.

These are pretty bad!

But there’s another less-discussed problem, too.

The Monoculture Problem

What would the best possible future look like? Essentially all extant views in population ethics give the same, surprising answer: create a monoculture. Find whatever life or experience generates the most value per unit of resources, then produce endless identical copies of it.

This implication has received remarkably little attention from philosophers. But I think it’s maybe as bad as any of the other problems listed above.

Consider two possible futures:

• Variety: A vast population of individuals leading very good lives, extraordinarily diverse in form, personality, interests, and accomplishments. No two individuals are identical. Inequality is limited — all lives are very good.

• Homogeneity: The same vast number of individuals, but each is a qualitatively identical copy of the best-off person in Variety.

Intuitively, Variety is better. A future containing only one life-type, repeated as many times as physics allows, feels impoverished — like a song with only one note.

Yet virtually all existing population axiologies prefer Homogeneity. Total utilitarianism does, because Homogeneity has higher total wellbeing. Average utilitarianism does too. Critical-level views do. Even egalitarian views prefer Homogeneity — it’s perfectly equal!

This follows from two principles that nearly all views accept: Pareto (if everyone is at least as well off, and someone is better off, the outcome is better) and Anonymity (only welfare levels matter, not who has them). Together, these entail that Homogeneity beats Variety. So essentially all extant impartial accounts of population ethics suffer from the monoculture problem.

What’s more, future technology will allow us to copy minds perfectly and search for maximally welfare-efficient designs. If so, standard axiologies recommend essentially producing just one optimal life-type as many times as possible. Endless galaxies containing nothing but the same blissful experience, repeated and repeated, would be the ideal.

The Saturation View

In light of these problems, I propose a new axiology: Saturationism. It's able to deal with all four of the problems I listed using the same basic machinery.

The core idea is that experiences¹ come in different types, defined by their qualitative characteristics — hedonic tone, complexity, representational content, and so on. These types form a kind of landscape, where similar types are closer together and dissimilar types are farther apart. When an experience comes into existence, it contributes intensity to its location in this landscape and to nearby locations.

The realisation value of a type is determined by both the wellbeing of the experience and by how many very similar experiences already exist. A region’s contribution to overall value is a concave function of the welfare-intensity at that region: the first instances contribute substantially, but additional near-duplicates contribute progressively less, approaching but never quite reaching an upper bound. A world’s total value is the integral of these contributions across the entire landscape.

Here’s an analogy. Imagine the space of possible experiences as a colour wheel, lit from above by an array of tiny lights. Each point on the wheel represents a possible type of experience — its hue corresponds to its qualitative character. When an experience comes into existence, it adds current to a light pointed at its location, illuminating that region.

Crucially, illumination is a concave function of current: the first instances make a region noticeably brighter, but additional near-duplicates contribute progressively less. There’s an upper bound on brightness that can never quite be reached.

A world’s value equals the total illumination across the wheel. On this view, Homogeneity concentrates all welfare in one region, lighting up only one small area. Variety illuminates the whole spectrum.

This structure makes diversity intrinsically valuable. Spreading welfare across many dissimilar types means each experience contributes at a steeper part of the concave curve, yielding more total value than concentrating the same welfare among near-duplicates would.

At small scales and with diverse experiences, the view behaves just like the total view. But at very large scales, the value of variety kicks in: it becomes increasingly less valuable to create an additional near-duplicate of some experience that has already been instantiated millions of times, and comparatively more valuable to create some wholly new form of positive experience.

Dissolving the Repugnant Conclusion

The classic path to the Repugnant Conclusion requires trading a utopian world for an enormous population of barely-positive lives. More precisely, the Mere Addition Paradox arises from three intuitive principles: that adding well-off people and improving existing lives is good (Dominance Addition), that more equal distributions with higher average welfare are better (Non-Anti-Egalitarianism), and that some sufficiently excellent world can’t be beaten by any world of barely-worth-living lives (Denial of the Repugnant Conclusion).

Once we accept the value of variety, we should reject the unrestricted versions of the first two principles — they fail when the “improved” world has much less variety. But we can accept variety-restricted versions.

Crucially, these restricted principles don’t generate the Repugnant Conclusion. To reach Z-world from A-world, you’d need a more equal, higher-average population that’s equally diverse while consisting wholly of barely-positive lives. But, on the Saturation view, barely-positive lives can only illuminate a tiny corner of the landscape. So no such world exists. The path to the Repugnant Conclusion is blocked.

Avoiding Fanaticism

Total achievable value is bounded above — there’s only so much experiential terrain to illuminate. That means no tiny-probability gamble can have arbitrarily high expected value.

Infinite Ethics

On Saturationism, the value of a world is finite and well-defined in any infinite universe — even if some locations have infinite wellbeing. Saturationism also discriminates between many infinite worlds that (for example) totalism treats as equivalent: a world that illuminates more of the landscape is better than one that illuminates less, even if both contain infinite welfare. What’s more, unlike other approaches to infinite ethics, it does not need to invoke the spatiotemporal structure of the universe or require a choice of ultrafilter, and therefore it avoids the problems that other do.

Separability

Like nearly all non-totalist views, Saturationism is non-separable — background populations can affect how we rank options. But this is a feature, not a bug. The value of variety just is an intuition that the correct axiology is non-separable.

Moreover, the violations are comparatively tame. If two populations have non-overlapping footprints in experience-space, their values simply add. At small scales, Saturationism approximates total utilitarianism. It’s only in unusual situations involving vast populations of near-duplicates that the totalist approximation fails.

Extant issues

There are still a lot of unresolved issues for Saturationism and, like any population axiology, it has unintuitive implications. Most importantly, the view’s implications in some highly-negative worlds are hard to stomach, though I think similar implications are unavoidable for any view that avoids fanatical implications.

Conclusion

If the Saturation View is right, then the best future isn’t the one where we’ve found the optimal experience and copy-pasted it across the cosmos. The best future is the one where we’ve gone exploring — where we’ve fully lit up the landscape of possible experiences. Not a single note, but a symphony.

This is a summary of a longer and more detailed write-up of Saturationism, which gives a “toy” version of the view to illustrate how it works before stating the full version formally. The full paper, with Christian Tarsney, is still work in progress.

1. I’ll focus on experiences, though the view could be defined in terms of lives or other “welfare events” (like instances of preference-satisfaction, achievement, and so on).