To make the analogy with the scale more accurate: suppose mass could also be negative (because welfare can be negative), and most of all: suppose Newton's law would use the measured mass, as measured on that scale. The latter would be a bit like quantum mechanics, as if the feather is in a superposition of different masses, and doing a quantum measurement with that scale gives its mass that enters Newton's law. Then the question whether the mass of the feather is positive or negative, is ill-defined when the feather is in a superposition of both positive and negative masses. 

A better physics analogy is Einstein's theory of special relativity. Suppose you and I have super accurate clocks. I determine that "now!" corresponds with time zero. Relative to my "now!", there are events in the past and future. But suppose you also determined your "now!" as time zero on your clock. And suppose the space-time event that corresponds with you saying "now!" lies outside the lightcone of my "now!" space-time event. The question is: is your "now!" in the future or the past of my "now!"? When the speed of light is finite, this question is always ill-defined, even if we had infinitely accurate clocks. You can always pick a reference frame according to which your "now!" exactly corresponds with time zero on my clock (yes, with infinite precision; what a coincidence!). And pick another reference frame according to which your "now!" is in the future of my "now!". In the analogy, the time of your "now!" on my clock, corresponds with the welfare of the nematode relative to non-existence. My "now!" corresponds with zero welfare of non-existence, your "now!" corresponds with the welfare of the nematode. If your "now!" is in the future (past) of my "now!", that corresponds with a positive (negative) welfare of the nematode. The different reference frames in special relativity correspond with different 'welfare frames' of the nematode. So even if a nematode could measure physical forces with infinite precision, and would be sensitive to the pain of the slightest increase in a physical force, it would still be impossible to say whether the nematode has a positive or negative welfare. I can compare my welfare with non-existence to a high degree, but not infinitely accurately. In the special relativity analogy, this corresponds with a space-time with a very high lightspeed. But for the nematode, the comparison with non-existence is much more difficult, which would correspond with a space-time with a very low speed of light. If the speed of light is extremely low, or say zero, almost all your space-time events are outside my lightcone, which means you can pick any moment along your timeline and I can pick a reference frame according to which that moment is in the future of my "now!". With the nematode: pick any full description of its experiences, the physical forces that it feels and so on, and I can pick a welfare frame according to which that nematode has a positive welfare, and you picked a welfare frame according to which that same nematode, with the very same experiences, has a negative welfare. There is no objective way to determine which of our welfare frames is the correct one. If a nematode's welfare range is very small, it is likely that all its experiences that it could possibly have always lead to a welfare level that is incommensurable with zero, even if the nematode could measure its own welfare with infinite precision. 

As for the TAI: the point is that I can give another equally reasonable/valid definition of a TAI as the one of Metaculus, and there is no objective way to determine which of our definitions is the correct one. This intrinsic indeterminacy of the definition results in the incommensurability of the timelines. I can always pick a definition according to which the arrival of TAI is after 2039, even if according to Metaculus' definition of TAI, the arrival is exactly in 2039 and we can measure that arrival date with infinite precision. The different definitions of TAI correspond with the different reference frames in special relativity, and the different welfare frames of the nematode. 

I expect if someone's welfare range is very small, it is more likely that its welfare is incomparable to (incommensurable with, on par with, neither better nor worse nor equal to) non-existence. When I look at my welfare, I try to imagine the average welfare W I would have over a period of say a month, that would make me indifferent between living that month versus non-existence. That welfare level W corresponds to 0 (by definition of zero welfare). Now imagine that same month, but with a tiny bit of extra happiness, for example the taste of one extra piece of chocolate. The welfare is W+dW (with W=0 and dW small). However, I think I would still be indifferent between living that month (with the extra chocolate) and non-existence. Hence, W+dW is also 0. In other words, my indifference curve is rather an indifference band. I believe I have such small indifference bands when it comes to comparing my welfare with non-existence. Now, the width of my indifference band is easily larger than your estimated welfare range of a nematode. You see where this is heading? If the nematode would have an equally wide indifference band as me when it comes to comparing its actual welfare with non-existence (and I have no reason to believe it is otherwise), and if its welfare range is smaller than this indifference band, then all its welfare levels are incomparable with non-existence, or indifferent from 0. 

The analogy with TAI timelines: there are many ways to define TAI, based on the set of capacities of the AI. Suppose I say that a TAI needs to have capacities S, and I believe those capacities are reached by the year 2030. Now you may have another definition of TAI, with another set of capacities S'. That will correspond with another timeline, say 2035. The crucial problem is: there is no objective way to determine which definition of TAI is the correct one. So there is no objective way to uniquely determine the timeline. There is rather a range of timelines.  

The crucial consideration is not about the welfare range, but about the welfare sign: whether a nematode's welfare is positive or negative. According to your reasoning, (animal) agriculture is very good if nematode's welfare is slightly negative and very bad if it is slightly positive, even if the welfare range is small. Some people believe the welfare sign is negative, others say it is positive, I expect most people believe it is around zero. There does not seem to be any consensus about the welfare sign. And we have no clue how we can possibly answer this question, what research method we could possibly use to determine the welfare sign. This is even more difficult than determining whether a nematode is sentient. I don't expect a solution the next decades. Therefore, I would say the welfare sign of a nematode is indeterminate: the question whether the welfare is positive or negative is ill defined. According to one reference frame, it is negative, according to another equally valid reference frame, it is positive. There is no objective, unique, absolute sign of a nematode's welfare. As in Einstein's special relativity, the moment 'now' for another observer (like the welfare 'zero' for another sentient being) is ill defined and depends on your frame of reference (e.g. whether you move towards or away from that observer). So in a sense it is meaningless to say a nematode's welfare is negative. This implies that we can basically neglect effects that change the size of the nematode population. Saying that animal agriculture is good or bad because it decreases the size of the nematode population, becomes meaningless. 

A small remark: your welfare range estimate has three significant digits, which I find very weird given the large uncertainty range. Instead of writing 6.68*10^-6, which gives a false impression of accuracy, I would rather write 'around 10^-5'. (I hate it when my students give overly exact estimates with many digits.)

Also: I tend to believe that, as with the welfare sign, a nematode's welfare range is not exact and has no unique, objective, absolute value. There is a range of valid values for the nematode's welfare range. The intensity of welfare experiences of a nematode and a human are intrinsically incomparable. Like asking the question whether 'i' (the square root of minus 1) is larger or smaller than 1: that is mathematically meaningless, because there are different, equally valid metrics one could use.

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. 

I haven't yet read the direct economic benefit studies: can you briefly say what are those extra jobs? I don't see why plant-based food production would be more labor intensive. And what types of jobs are those? High or low-skilled jobs?

My arguments why meat offsetting is impermissible (and hence personal veganism is a moral duty): https://stijnbruers.wordpress.com/2019/08/22/carbon-offsetting-versus-meat-offsetting/

I'd like to see a few more surveys on moral weights, with larger samples of both animal welfare experts and lay people, than this small one (n=100) I conducted in Belgium https://brill.com/view/journals/jaae/7/1/article-p91_6.xml

Have to read the study, but reminds me of what I called the moral gravity bias https://stijnbruers.wordpress.com/2014/08/08/the-moral-gravity-bias/

I expect animal welfare in D to be higher than in C, almost by definition. In D, the purpose is to have as many animals as happy as possible, without killing them. Whereas in C, the prime objective remains killing and eating the animals. The farmers do not intend to maximize the welfare of the farmed animals. The population in D may be lower than in C, but the population size in D is chosen to maximize animal welfare, whereas the population size in C is chosen to maximize farmers profits. If population size in C is larger than in D, the welfare of the animals in C is suboptimal.

With choosing option C for others, I actually meant not trying to reject option C for others, e.g. not campaigning against option C, not spending money on trying to switch people to option A instead of option C. I agree that the most cost-effective invertebrate welfare interventions are more effective than interventions to switch people from B to C. Or, if you want, you can add another option B’, which is similar to B but with reduced animal suffering. Your favorite invertebrate welfare interventions correspond to switching people from B to B’, and that might at the moment be more effective than switching them from B to C. 

Thanks for the conversation!

Hi Vasco,

Perhaps I understand your position. Here is a line of argument that results in your conclusion based on total utilitarianism. Suppose for simplicity every individual can choose between four options:

A: veganism: not buying and eating animal products. This option generates the second lowest total welfare, higher than option B.

B: unhappy animal farming: buying and eating products from factory farms where animals live unhappy lives. This generates the lowest total welfare.

C: happy animal farming: buying and eating products from farms where animals live happy lives. This option generates the second highest total welfare, lower than option D but higher than A and B.

D: animal sanctuary: eating vegan and donating money to a sanctuary that breeds animals and give those animals long and very happy lives. This generates the highest welfare.

In terms of total welfare, we have D > C > A > B. Therefore, if everyone was total utilitarian, everyone should choose D. In extremis, total utilitarianism entails that everyone should sacrifice themselves a lot in order to bring into existence huge numbers of very happy animals that live on a sanctuary. However, if only you are total utilitarian, then according to act utilitarianism it would be wrong for you to choose D when other, non-utilitarian people are extremely reluctant to choose D. Sidenote: if you were a rule utilitarian instead of an act utilitarian, you could have to follow the rule that everyone has to follow, namely choosing option D, even if other people do not follow that rule (i.e. do not choose that option D). So I assume you are an act utilitarian.

There are two things to consider: which option you should choose for yourself, and which option you should choose for other people. I’ll argue that you should choose option A for yourself and, importantly, option C for others.

As a total act utilitarian, you should choose option A for yourself. Sure, option A is dominated by options D and C. But those two options are more expensive: in C you have to pay extra money for the meat, because meat from happy animals is more expensive than vegan products and meat from unhappy factory farmed animals. In option D you have to donate money to the sanctuary. However, it is very likely that donating your money to the most cost-effective animal welfare charities improves total welfare more than donating that money to an animal sanctuary or a farm where animals are happy. In particular, the extra money that you would spend on high-welfare meat when you choose option C, could better be spend on effective campaigns to transition people from option B to C.

This brings me to the second issue: which option should you choose for other people? Most people currently choose option B. Persuading them to choose option C might be feasible with campaigns that require a bit of money, whereas shifting people to option D might be unfeasible, no matter how much money you throw at such a campaign. At first sight, total utilitarianism seems to suggest that the best strategy is to have people switch to option D, but that may be unfeasible or too costly. Note that in terms of total welfare, it is better to persuade people to choose option C instead of option A. 

So there you have it: choose veganism for yourself and happy meat for others. That would be the conclusion of a total act utilitarian.