One interesting thing about the causal impotence objection to ethical vegetarianism is that, so far as I can tell, almost no ordinary person subscribes to it. (Roughly, the causal impotence objection notes that while the meat industry is sensitive to large fluctuations in demand, it’s not sensitive to the sort of fluctuation in demand that results from a single individual going vegetarian.) That is to say, almost everyone agrees that if it is wrong to needlessly kill animals for food, then it is wrong for them to eat the flesh of animals that have been needlessly killed for food. I suppose this must be because most people don’t think about such issues with a consequentialist vocabulary, and you’ll only really be inclined to find this conditional worrisome if you do. I’m personally satisfied that the conditional is true, as it seems sufficiently analogous to conditionals like “if it’s wrong to needlessly kill dogs for their hides, it’s wrong to wear dog-hide shoes”, but we might want a stronger justification than an analogy.
Here’s a slightly suspicious way of getting around causal impotence. Let φ = animals are needlessly killed for food, ψ = you eat the flesh of animals that have been needlessly killed for food.
- ~φ → ~ψ
(3) follows from (1) and (2) in SDL. Consequentialists who care about the suffering of sentient creatures should accept (1), and everyone should accept (2). So such consequentialists who also deny (3) are committed to rejecting the move from (1) and (2) to (3). This means rejecting either modus ponens, or one of the following axioms of SDL:
A1. If p, then O(p)
A2. If O(p → q), then O(p) → O(q)
This is slightly interesting. Take it for granted that going vegetarian is causally impotent. Then lots of consequentialist normative theories will say that going vegetarian is not obligatory, though they will say that it is obligatory that animals not be needlessly killed for food. The normative theory and SDL appear to conflict. (If I had to guess, someone who denies (3) would probably want to reject (A2), since it seems to be doing the most work in generating the controversial missing premise.)
That’s kind of embarrassing, but I don’t think it’s the only (or the correct) way to respond to the argument. Rather, I think you ought to say that accepting (3) doesn’t commit you to accepting that there’s an obligation to go vegetarian. It just commits you to accepting some sort of obligation to falsify ψ. As it turns out, there are a number of ways to falsify ψ. One is going vegetarian. Another is making it the case that animals are not needlessly killed for food. When there are two ways of satisfying an obligation, you should choose the one that your normative theory sanctions — from a consequentialist point of view, the one that is causally efficacious in promoting value and minimizing disvalue. That’s not going vegetarian, if going vegetarian is in fact causally impotent.