Hey Philosopher folk: Do you know of any viable or at least well-examined arguments ever proposed that conclude that one murder (or some equivalent malfeasance) is no better nor worse than 8 million murders? Or generally, that multiple instances of a wrongdoing have no greater or lesser value of any kind, apart from numerical? If not, could anyone conceive of a possible argument for this? Please note, I am not a serial killer or mass murderer, this question just arose in a debate about an unrelated topic.

Well, I'm glad to hear you are not a murderer. If you were, I would argue that it is worse to kill greater numbers of people like this:
1. If act or outcome A is morally wrong, then A x n (n number of As) is more morally wrong than A. [stronger version might say A x n is n times morally worse.]
2. Murder is morally wrong.
3. So, n murders are morally worse than one murder. [Or any greater number of murders is worse than just one, perhaps n times worse.]

Like most good arguments, this one just puts things in a good form for us to be able to consider the premises. It sounds as if you (like me) accept premise 2. So, what justifies premise 1? The easiest way to justify it is if one is a utilitarian (or other consequentialist) who measures wrongness in terms of bad consequences or outcomes. So, if one murder causes X amount of bad consequences (e.g., suffering, loss of potential flourishing for victim, etc.), then n murders would cause (roughly) nX bad consequences. And it would be morally worse [n times worse] for that reason.

But on just about any moral theory, more wrong acts or outcomes is worse than fewer. If a Kantian says one murder is wrong because it violates the categorical imperative (it cannot be universalized, and it treats the victim as a means not an end), then she will also be able to say that Hitler's (helping to cause) 8 million murders is much worse, because he has done something wrong many more times.

Maybe the basic support for premise 1 is a powerful moral intuition that seems hard to deny.

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