A common formulation is that the "rules" are the ones which if generally adopted as a moral code would maximize expected utility: i.e. there is a form of "best" or "ideal" moral code.
However, this can lead to cases where an act which would (by itself) maximize expected utility would also be in violation of the ideal moral code. So the act would be "right" from an act utilitarian point of view, but "wrong" from a rule utilitarian point of view.
Relevant examples here could include torturing someone "for a greater good" (such as to stop the infamous ticking time bomb). The logic for torture in such cases seems very sound from an act utilitarian perspective; however, an ideal moral code would have a rule of the form "Don't torture anyone, ever, for any reason, no matter if it appears to lead to a greater good". This, incidentally, is one resolution to Torture vs Dust Specks.
Right, but if the moral code is really ideal on consequentialist grounds and following the rules really leads to better expected outcomes for humans than not doing so, even when it appears otherwise, then the act consequentialist should also agree that you should follow the rule even when it appears to be sub-optimal.
On the other hand, if the claim is that an ideal reasoner with full knowledge should follow the rule even when it provably does not maximize expected utility, then that's a form of deontology and a consequentialist should disagree.
Despite being (IMO) a philosophy blog, many Less Wrongers tend to disparage mainstream philosophy and emphasize the divergence between our beliefs and theirs. But, how different are we really? My intention with this post is to quantify this difference.
The questions I will post as comments to this article are from the 2009 PhilPapers Survey. If you answer "other" on any of the questions, then please reply to that comment in order to elaborate your answer. Later, I'll post another article comparing the answers I obtain from Less Wrongers with those given by the professional philosophers. This should give us some indication about the differences in belief between Less Wrong and mainstream philosophy.
Glossary
analytic-synthetic distinction, A-theory and B-theory, atheism, compatibilism, consequentialism, contextualism, correspondence theory of truth, deontology, egalitarianism, empiricism, Humeanism, libertarianism, mental content externalism, moral realism, moral motivation internalism and externalism, naturalism, nominalism, Newcomb's problem, physicalism, Platonism, rationalism, relativism, scientific realism, trolley problem, theism, virtue ethics
Note
Thanks pragmatist, for attaching short (mostly accurate) descriptions of the philosophical positions under the poll comments.
Post Script
The polls stopped rendering correctly after the migration to LW 2.0, but the raw data can be found in this repo.