Three Arguments for Consequentialism
Including a Master Argument to rule them all, find them, bind them, etc.
This post will set out three arguments for consequentialism (or against deontic constraints), in order of increasing abstraction. You should probably accept all three.
Utilitarian Pre-commitment vs Deontological Defection
From behind a veil of ignorance, everyone in the situation would rationally endorse killing one to save five, since that markedly increases their chances of survival. This means that each person has decisive reason to pre-commit their conditional consent to be killed, in the event that they are in the position of the one, on condition that the others do likewise. So now consider the following argument:1
If everyone affected consensually pre-commits to this plan, then one ought to kill one to save five.
If people lack the opportunity to communicate in advance, but have decisive reason to pre-commit to a co-operative agreement (e.g. of mutual conditional consent to the above plan), then one ought to enforce this rationally-mandated pre-commitment in an unbiased fashion.2
Before opening our eyes for the first time, we all have decisive reason to pre-commit to endorsing utilitarian tradeoffs (conditional on others doing likewise), as this maximizes our expected welfare.
So: one ought to enforce utilitarian tradeoffs (in an unbiased fashion).
Deontology is defection. Once you know you’re rich, you no longer want to give to the poor. Once you know you’re on top of the footbridge, you don’t want to save the five on the tracks. But if the shoe were on the other foot, you’d think differently. And the rest of us have no reason to enshrine your status quo privilege. We should stick to what we would all have agreed to before we knew our positions in life. *Push*
The Teleological Argument
Our reasons for action are given by applying instrumental rationality to the correct moral goals.
No competing candidate moral goals are more important, in principle, than saving and improving lives.
So: we should do whatever would best save and improve lives.3
The “Master Argument”
Moral philosophy progresses via reflective equilibrium: weighing the plausibility of a theory’s fundamental principles against that of its verdicts about cases.
So consequentialism wins out: it has very strong reasons in support, and no clear reasons against.
The latter clause is intended to rule out discretionary enforcement, e.g. killing the one if and only if it turns out to be Bob. Such a system would obviously no longer be in Bob’s ex ante interests.