No rule for turning individual preferences into social choices can satisfy unrestricted domain, the Pareto principle, and even a minimal right for each person to decide one private matter.
Sen proved it in 1970 with two people and one book. Prude would rather nobody read Lady Chatterley's Lover, but would rather read it himself than let Lewd read it. Lewd would rather Prude read it than read it himself. Give each man the right to decide about his own reading and the outcome conflicts with the ranking both men agree on. Rights over private matters and unanimity cannot both be honoured by the same rule.
In practice
- A platform promises users control over their own feeds and the outcome everyone says they prefer, and finds it has to break one of the promises.
- A household rule that each person chooses their own dinner meets a night when both would rather eat the other's choice.
- Standing
- A proved impossibility rather than an empirical claim, and one of the standard results in social choice beside Arrow's impossibility theorem. Compare the paradox of tolerance for the political version of the same tension.
- Further reading
- Wikipedia
- Subject
- Law & Politics
- Essay
- What can be proved and measured about power