An argument against vegetarianism that I’ve encountered a few times is that any individual’s consumption decisions will have no effect on the actual production of meat, and so are ineffective. In particular, this argument was made recently at Bad Conscience.

This argument cannot be right.

We know that production decisions are based, ultimately, on sales and hence on demand. The proponents of this argument accept this, by granting that if everyone stopped eating meat, there would be no meat production (or barely any).

How sensitive are production decisions to demand? Either they are precisely sensitive – they can pick up the signal from each individual purchase and respond to it – or they are crudely sensitive – they use approximate, gross, indicators, perhaps involving hundreds of individual purchases as a single data-point.

If the former, then each vegetarian is directly responsible for preventing the manufacture and destruction of all the animals they would otherwise eat in their life – which is a large number.

The anti-vegetarian argument focuses on saying that this is not the case – markets are not this precisely sensitive, and if (as is implied) vegetarians think they are, then vegetarians are idiots.

But even if markets aren’t precisely sensitive, they must have some sensitivity – crude, rough, sensitivity. But the sensitivity still governs the same effects – does meat get produced, and if so how much. This means the same total effect is divided up among the consumers, just divided more roughly and unevenly.

This means that some purchases will have no effect – but only because other purchases have more effect, disproportionate effect. And since we can’t tell which our purchases will be, each one still on average has their proportionate effect of preventing a large number of individuals killings.

Ducks

This is just maths. Let me do some tables.

Suppose there are 10 people, who each year eat a total of 100 ducks. The ducks are killed only to feed these people. 0 duck-eaters: 0 ducks killed. 10 duck-eaters: 100 duck killed. This is (analogous to) what everybody accepts – the two extreme points. The incomplete table looks like this →:

In a sensitive system, each individual could reduce the number of killings by 10. There would be this table ←:

Now suppose – as the anti-vegetarian argument asserts – that this isn’t the case. In fact, when the first of these ten people go vegetarian, it makes no difference to how many ducks are killed. Suppose the same holds for the second and third people as well. This gives our incomplete third table↓:

See how you still have the gap between 0 ducks killed and 100 ducks killed? That change has to occur at some point, wherever the change comes. For instance, the table might look like this ←:

Here, vegetarians 1-3 make no difference, as do the 5th, 7th, and 9th. But the 4th vegetarian saves 40 lives, and the 6th, 8th, and 10th save 20 each. So most vegetarians have no effect – but the average effect is the mean of 40, 20, 20 20, 0, 0, 0, 0, 0, and 0. Which =10. That is, the vegetarians have exactly the same average effect as in the sensitive system.

At risk of belabouring the point, suppose a different, very ‘rough’ system, with systematic irrationalities, as here →:

Here, two vegetarians have no effect at all, and three (the 3rd, 5th, ad 7th) actually increase the number of ducks killed. But what’s the average number of ducks saved per vegetarian?

Mean of 0, 0, -10, 29, -19, 50, -12, 42, 13, 7 = 10!

Noticing a pattern? It’s always 10! That’s because if everyone being vegetarian eliminates all meat production, which everyone in this dispute accepts, then the average effect of being vegetarian must always be the total meat production divided by the number of people who need to go veggie (in this example, 100/10).

Now, sometimes we shouldn’t act based on averages. For instance, if the 7th person in the last system knows how the system works, and knows that the last two people are definitely not going to become vegetarian, then they shouldn’t go vegetarian because they know they’ll cause an increase in killings (by whatever mechanism).

But that’s because they know the details of where they are in the system. Typically, consumers don’t. This is analogous to voting: my one vote could have no effect, or it might be a crucial decider that has a disproportionate effect, and I can’t know in advance. In this situation, I have to act based on what the average expected result is.

Of course, it might be that the people who use this argument against vegetarianism know where the critical points come. But that implies they know when, where, and how to have maximum, exaggerated effect on meat-production. They should tell us.

One last time: if N people doing x would produce total result R, the average effect of doing x is R/N. For vegetarianism, that means a dozen or more killings prevented per year.

The maths is simple: reality is complex, but when we can’t trace out the complexities we must act on whatever simple maths is available.

I’m aware that I’m starting to sound like Paul in his post: my argument is just so obvious, so evidently true, that I can’t understand how anybody could fail to accept it. Just as he feels about his opposite argument. One of us is wrong, despite our shared confidence. All I can say to this is that the one who’s right is probably me, because I’ve got tables.