From Planet of Hats  #28, by David Morgan-Mar

From time to time, public interest flares up in a thought experiment invented to illustrate a problem in ethical theory. It’s something utilitarians came up to answer deontologists. Deontologists are ethicists who think that some actions are wrong simply because they are always wrong.  It is supposed to be a comeback in a conversation utilitarians fantasize about having. The deontologist gives “murdering a baby” as an example of an action that is always wrong. The utilitarian comes back with, “What if the baby is Hitler and you’re a time traveler? You could prevent the Holocaust and World War Two by murdering that baby!”

To which a wide variety of responses are of course possible. What always gets me about it is the same thing that gets me about utilitarianism generally, which is that it requires people to act on the basis of knowledge which is not in fact available to humans. In order for a utilitarian to know how to act, that utilitarian would have to find himself or herself in some ludicrously improbable situation. The fondness of utilitarians for thought experiments that require the total isolation of the hypothetical from any context is symptomatic, not only of the nature of philosophy as a profession, but also of the impossibility of performing any form of the hedonistic calculus in the circumstances of actual human life.

Bulking large in the context from which this particular experiment requires us to isolate the hypothetical are the implications of the idea that the agent is capable of time travel. I’ve tweeted about this several times. Here is the most recent example:

Other people also think it is silly. Here is a series of short-short stories about Hitler-killing in the form of a Wikipedia talk page. Some excerpts:

At 18:06:59, BigChill wrote:
Take it easy on the kid, SilverFox316; everybody kills Hitler on their first trip. I did. It always gets fixed within a few minutes, what’s the harm?

At 18:33:10, SilverFox316 wrote:
Easy for you to say, BigChill, since to my recollection you’ve never volunteered to go back and fix it. You think I’ve got nothing better to do?

11/16/2104
At 10:15:44, JudgeDoom wrote:
Good news! I just left a French battlefield in October 1916, where I shot dead a young Bavarian Army messenger named Adolf Hitler! Not bad for my first time, no? Sic semper tyrannis!

At 10:22:53, SilverFox316 wrote:
Back from 1916 France I come, having at the last possible second prevented Hitler’s early demise at the hands of JudgeDoom and, incredibly, restrained myself from shooting JudgeDoom and sparing us all years of correcting his misguided antics. READ BULLETIN 1147, PEOPLE!

At 15:41:18, BarracksRoomLawyer wrote:
Point of order: issues related to Hitler’s service in the Bavarian Army ought to go in the World War I forum.

Here’s an SMBC:

I’m particularly fond of this xkcd:

There’s also some good stuff on the TVTropes page about time travelers killing Hitler.