Thanks to everyone for the discussion here. A few replies to different strands.

First, I agree with Vasco that transparency matters. However, transparency isn’t the only good—and, unfortunately, it often competes with others. (Time is limited. Optics are complicated. Etc.) So, by Vasco's own lights, it's only plausible that organizations should devote scarce resources to answering this particular cause prioritization question—and then post their answer publicly on the Forum—if they think (or should think) that the expected value of so doing is positive. It isn’t obvious that anyone in these organizations thinks (or should think) that’s true. 

Second, you can use our work on welfare ranges without buying into naive expected utility maximization. I assume that many people who use our welfare ranges are averse to being mugged and, as a result, adopt one of the many strategies for avoiding that outcome. So, it can be true that (a) the expected value of impacts on some group of animals is very large in expectation and (b) you aren’t rationally required, by your own lights, to care much about that fact (and, by extension, investigate it in depth or engage on it publicly).

Third, our models have a narrow theoretical and pragmatic purpose: we wanted to improve the community’s thinking about cause prioritization regarding a group of animals where we took there to be good evidence of sentience. We don’t think you can take our models and apply them generally, nor do we think you can ignore the specific purpose for which they were developed. Put differently, once some animals have crossed some threshold of plausibility for sentience, we support using our models with trepidation, largely because we don't have better options. But you shouldn't apply the model beyond that and, if you have any other principled ways to make decisions, that's probably better. (Principled: “We think that any theory of change for the smallest animals begins with key victories for larger animals.” Unprincipled: “We don’t like thinking about the smallest animals.”)

Fourth, we disagree with @NickLaing characterization of the Moral Weight Project as stacking the deck in favor of high welfare range estimates. There are two reasons why. One of them is that the MWP does not say, “Sum the number of proxies found for a species and divide by the total number of proxies to get the welfare range.” If that were true, then the number of proxies would straightforwardly determine the maximum difference in welfare ranges. But that isn't correct. We have models (like the cubic model) where you need to have lots of proxies before you have a "highish" welfare range. However, we have lots of models, with uncertainty across them. Predictably, then, more moderate estimates emerge rather than any extreme (whether high or low). Someone is free to say: "A better methodology wouldn't have been so uncertain about the models; it would have just included animal-unfriendly options." That's clearly tendentious, though, and we think we made the right call in including a wider range of theoretical options. That being said, we’ll reiterate that those who are interested in the details of the project should examine the particulars of each model and its conclusions rather than just taking the overall estimates straightforwardly. You can find each model’s results here. 

The second reason we disagree with Nick’s characterization of the MWP is that, even if you isolate a particular model, you don’t automatically get high welfare ranges. Suppose, for instance, that there are 80 proxies total and that a model uses them all. If there were N that were as simple as "any pain-averse behavior," then, for the core models of the MWP, saying "likely yes" to each of them would give you a sentience-conditioned welfare score of 0.875*N/80 on average. We didn't consider animals as simple as nematodes in the MWP because we didn't think that the methods were robust for that type of animal. (See above.) But say you think there's a 0.5% chance of sentience for nematodes. Then, the sentience-conditioned welfare range would have been approximately 0.005*0.875*N/80. If the average model had 5 proxies that are as simple as "any pain averse behavior" and we gave "likely yes" to nematodes on all five, that would generate a mean welfare range of 0.005*0.875*5/80 = 0.00027. Again, we don’t endorse using the MWP for animals with that small of a probability of sentience, but 0.00027 isn’t a particularly high welfare range. (And as we've said many times, we’re just talking about hedonic capacity, not “all things considered moral weights,” which don’t assume hedonism. That number would be lower still.)

Should we find funding for a second version of the project, we’re likely to take a different approach to aggregating the proxies to produce welfare ranges, aggregating welfare ranges across models, and communicating the results. Still, we hope the first version of MWP contributes to more informed and systematic thinking about how to prioritize among different interventions.

Even just the effects on wild insects could be important, so anyone who is interested in insect welfare should be interested in these effects, too, or have good reason to ignore them, which I'd be interested in knowing (and possibly challenging).

I'd also tentatively put mites, springtails and farmed insect larvae at similar welfare ranges and probabilities of sentience, although quite uncertain. So, if you count farmed insect larvae as worthy of moral consideration at all, you should probably count mites and springtails, too, and to similar degrees on welfarist grounds.

I think some potentially good reasons to ignore the effects on wild terrestrial invertebrates are the following:

1. You think we'll have much larger expected impact on invertebrates with the invertebrate work we (or you) support or will support. Maybe (y)our portfolio of interventions will be positive in expectation across groups of welfare ranges and probabilities of sentience.
   1. I think this requires at least comparing to estimates of the effects of vertebrate-targeting interventions on wild terrestrial invertebrates, e.g. Vasco's, to be justified. So you aren't exactly ignoring the effects at all. That ~36% of the world's habitable land is used for animal agriculture, directly or for feed,^[1] seems like a good reason to believe that animal agriculture is one of the main ways we affect wild (terrestrial) invertebrates and that some of the highest leverage vertebrate interventions will be among the highest leverage for wild invertebrates.
2. You think the impacts on wild terrestrial invertebrates are generally good anyway, but don't differ enough between interventions to outweigh reasons for sometimes prioritizing vertebrates (e.g. normative uncertainty or a portfolio that's robustly good across sentience and welfare range groups).
   1. I'd want to know why. I have some doubts for animal product reduction, e.g. work to support alternative proteins and veg food advocacy.
3. You're clueless about the effects on wild terrestrial invertebrates (e.g. given uncertainty about their expected average welfare, or tradeoffs between natural deaths and crop deaths) and you ignore them on the basis of cluelessness, using imprecise credences.
   1. Even as someone suffering-focused, I'm currently clueless about the expected effects of crop agriculture on wild terrestrial invertebrates. It seems like pesticide deaths could be far worse than natural deaths, generally at least as intense at their worst as natural deaths and often more drawn out, enough to make up for and possibly outweigh the reduction in population sizes. I think the (expected) effects could go either way, and we probably need more primary research to decide which way.
      1. However, I do think beef/grazing/pasture reduces wild terrestrial invertebrate suffering. So, if you're ignoring some effects, it seems like you should separate the crop and pasture effects and deal with them separately. They affect different individuals living in different areas.
   2. FWIW, this is not the same as assuming the expected effects are precisely 0 and then ignoring them because of that. It would be an incredibly suspicious coincidence if the expected effects were exactly 0. You'd have to ignore (almost) all evidence about the actual lives of these animals and the effects of agriculture, and rely (almost) entirely on a symmetric prior, and that doesn't seem justified to me.
4. Non-consequentialist / non-welfarist reasons.
   1. I don't personally consider these to be good reasons, but I see ethics as mostly subjective, so they can be good reasons to other people.

1. ^{^}

   7% for crops for direct human consumption, 1% for urban and built-up land, including settlements and infrastructure, and 12-13% for logging for wood. I expect almost all of the rest of habitable land to be left alone, some possibly abandoned and allowed to rewild.

I'm right on the side of ignoring the effects on tiny creatures.

1. I don't think Rethink's calculation techniques work as well for smaller animals as for larger ones. As I've discussed before, BOTH their sentience ranges and their behavior scores rely heavily on the presence of pain response behavior. This means if a creature have any pain averse behavior (like just withdrawing from anything), it is guaranteed a highish welfare range. If it has a few of these behaviors the numbers get high fast. Their methodology doesn't really have scope for tiny welfare ranges.

2. By my lights I consider this a mugging: I don't consider probabilities this small (for me probability of sentience is <0.0001) worth considering in calculations. Everyone has a different "mugging threshold" as it were, and for me this falls below that. If I bought RP's sentience probability of 0.07, I wouldn't consider this a mugging.

3. Net Positive lives: On the off chance these creatures are sentient, I think they most likely have net positive lives for a few reasons. 

First I buy many of the arguments in this article that both wild animal deaths and lives aren't as bad as are often claimed. 

Second if we're going to index welfare ranges on human behavior, why don't we index animal wellbeing on human wellbeing? I feel like its a bit "choke on your cake an vomit it too" to suggest that animals are much like humans in their sentience and ability to experience pain, yet don't have similar positive and negative ranges of experience that usually end up net-positive for humans, even those who live in pretty tough situations? I get this is a bit basic...

Third soil nematodes mostly just go about their business, and aren't necessarily under the continuous stress that wild prey are like deer or mice are, where I think there are better arguments for wild animal net-negativity. Yes they have plenty of predators, but I don't think they don't spend a huge proportion of their efforts avoiding them.

4. I'm not just a consequentialist utilitarian. Enough said and on this note I appreciate the recent article by @Rethink Priorities and @Marcus_A_Davis which claims we should be more uncertain about our philosophical judgements.

I buy most of @Michael St Jules 🔸 top 3 arguments as well, which are mostly practical considerations downstream of mine. I suspect he would disagree with my 3 considerations above (but could be wrong).

I think its reasonable to talk about why they are excluded, but in many cases it might be better EV not to communicate it, even when the org has considered these creatures in its calculation. The general public might well distrust orgs that consider these creatures' welfare. Like @Henry Howard🔸 said it can look crazy, but not only that, for most people it can rightly seem offensive or cruel to consider microscopic creature's welfare taking precedent over the welfare of humans or even larger animals. I have graet sympathy for people who criticize our community for indulging in discussions like this.

I could be convinced in the other direction through more compelling research that disagrees with my consideratoins above, but I think its unlikely to be forthcoming in the near future.

Organisations using Rethink Priorities’ mainline welfare ranges should consider effects on soil nematodes, mites, and springtails.

The only argument I can think of against this would be optics. To be appealing to the public and a broad donor base, orgs might want to get off of the train to crazytown before this stop. (I assume this is why GiveWell ignores animal effects when assessing their interventions’ impact, even though those swamp the effects on humans.) Even then, it would make sense to share these analyses with the community, even if they wouldn’t be included in public-facing materials.

I think most views where nonhumans are moral patients imply these tiny animals could matter. Like most people, I find the implications of this incredibly unintuitive, but I don’t think that’s an actual argument against the view. I think our intuitions about interspecies tradeoffs, like our intuitions about partiality towards friends and family, can be explained by evolutionary pressures on social animals such as ourselves, so we shouldn’t accord them much weight.

I don’t know much about nematodes, mites or springtails in particular, but I agree that, when thinking about animal welfare interventions, one should be accounting for effects on wild animals.

(As Vasco says, these effects plausibly reverse the sign of factory farming—especially cattle farming—from negative to positive. I’m personally quite puzzled as to why this isn’t a more prominent conversation/consideration amongst the animal welfare community. (Aside from Vasco’s recent work, has ~any progress been made in the decade since Shulman and Tomasik first talked about the problem? If not, why not? Am I missing something?))

Organisations using Rethink Priorities’ mainline welfare ranges should consider effects on soil nematodes, mites, and springtails.

1. Reductio ad absurdum: If we consider the lives of nematodes and mites meaningful, suddenly all human welfare questions become meaningless compared to the question of how our behaviour affects nematode/mite welfare. The conclusion will be that we either need to nuke ourselves or completely restructure society around maximising nematode wellbeing. This is impractical, and like many internally consistent but impractical philosophies (nihilism, antinatalism, Kaczynskiism) aren't conducive to a functioning society.

2. Poor analysis: The calculations are always the same: huge numbers multiplied by tiny numbers, all of which are highly uncertain and unlikely to become more certain with "more research" (highly doubt any study is going to illuminate the moral value of mite suffering)

3. Looks crazy: Even mentioning the issue to say why it doesn't matter has a significant cost: the fact that it was considered seriously enough to warrant rebuttal makes the organisation look crazy to normal people, in the same way that Rethink Priorities running an analysis on whether nuking Australia would be net good or bad would look crazy.

I got a probability for this of 58.7 %

This seems to me like a Pascal's mugging. Much has been written about why we should not concede to such. To me, it is enough to see that history has not been kind to those who, when faced with a speculative moral analysis in conflict with human values, chose the analysis.

To ask that others prioritize the well-being of nematodes over that of clearly sentient animals (including humans), I'd need far greater confidence in the ability for these small beings to suffer. To prioritize reducing their populations, I believe we need much more confidence that their lives are net negative, and that downstream effects could be avoided. (Even with those considerations, I think there's still some moral uncertainty. Beings with net-negative welfare can still want to live, and their lives have value in non-utilitarian moral perspectives.)

Organisations using Rethink Priorities’ mainline welfare ranges should consider effects on soil nematodes, mites, and springtails.

I appreciate you championing this view Vasco, despite all the pushback. I found your reasoning pretty convincing, and it seems to me like if it's wrong, it will be because of more general philosophical problems with utilitarianism or expected value reasoning. 

Organisations using Rethink Priorities’ mainline welfare ranges should consider effects on soil nematodes, mites, and springtails.

I think Jonathan Birch's precautionary principle is a reasonable, risk-averse (in all directions) way to go about weighing up these risks. On this framework, some suspicion that a being might be sentient is reason to treat it as a research priority - but not to change public policies, for which there is a great cost. So yes, please someone do research on the sentience of these creatures. But I don't think that charitable organizations should be changing policies just yet.

There are several reasons why they shouldn't:
1. People are very bad at thinking in small or large numbers. When told to name a percentage, instead of saying 0.00014%, they are more likely to say 1, or 5%, because they know it's not 0% and whole numbers are easier to think about. In other words: I take RP's sentience estimates with a large grain of salt.
2. If we did take a pure expected-value approach, I think we would find ourselves being mugged in  in many situations, and our whole lives would be quite different. And we would likely make many mistakes, due to the bias mentioned above. For this reason it's pragmatic to not purely maximize expected utility, but to favor 'safe bets'.
3. As others here have mentioned, organizations need to think about their PR, and their PR relies on acting on reliable evidence, not small probabilities. Given that RP's welfare ranges are meant to inform such organizations, they too should err on the side of certainty.
4. RP's welfare ranges inform animal welfare interventions. But when trying to improve animal welfare, we need to think not only about proximate impacts, but also a long-term theory of change. Changing minds and ending speciesism is an integral part of a long-term theory of change for animals, whether that ultimately includes nematodes or not. In the short term being overly radical or strange may be more likely to alienate supporters, thereby harming the movement's progress in the long run.

I didn't 100% disagree with the first question because 1) merely "considering" is probably good 2) I do think it's possible these animals are sentient and 3) I'm not totally sure about my arguments

Organisations using Rethink Priorities’ mainline welfare ranges should consider effects on soil nematodes, mites, and springtails.

So long as expected welfare is appropriately discounted based on reasonable guesstimates of sentience. 

Organisations using Rethink Priorities’ mainline welfare ranges should consider effects on soil nematodes, mites, and springtails.

Although I’m not an expert my current belief is that the welfare of these things doesn’t matter at all because their utility = 0.  Also, the article suggests that the people supporting this are fine with eliminating much of the world’s biodiversity, and I think that would be terrible.

The crucial consideration is whether those small invertebrates have a positive or negative welfare significantly different from zero. My best guess is that for those animals, their average welfare is incommensurable with zero, where zero represents the welfare in the state of non-existence. That means a nematode with welfare X can be considered equally good as a non-existing nematode, and increasing that nematode's welfare to X+dX can still be considered equally good as non-existence. In this case, we can neglect population-changing effects on soil nematodes. The effects of agriculture on nematodes are such population-changing effects (agriculture decreases the population sizes of small soil invertebrates), and hence can be neglected. 

Vasco, do you consider it evidence for or against a theory that it doesn't have recommendations that involve large amounts of destruction of humans? I feel like you have a tendency to dodge this issue when pressed on it by just repeating that your view doesn't in fact recommend supervillain type stuff given practical current constraints. But that leaves open the question of what you would do if those constraints were loosened somehow.