I feel so happy that “what’s your crux?” / “is that cruxy” is common parlance on LW now, it is a meaningful improvement over the prior discourse. Thank you CFAR and whoever was part of the generation story of that.
“Is that cruxy” approximately means “is this proposition load bearing for your opinion on the broader topic we are discussing?”. I.e. if you are discussing whether god exists, and then in the process of that hit the question of whether historical Jesus was real, then one person can say “is this cruxy?” to mean “would you actually change your mind (or at least substantially update) on whether god exists if historical Jesus did in fact exist?”.
See the crux tag. Duncan Sabien wrote the CFAR handbook’s double crux essay, etc.
A crux for a belief B is another belief C such that if I change my mind about C, that will also change my mind a lot about B.
E.g., my cruxes for “it’s raining” might include things like “I’m outdoors and can see and feel lots of water falling from the sky on me”, “I’m not dreaming”, “I don’t think aliens are trying to trick me”, and so on.
I don’t natively think in terms of cruxes. But there’s a similar concept which is more natural for me, which I’ll call a delta.
Imagine that you and I each model the world (or some part of it) as implementing some program. Very oversimplified example: if I learn that e.g. it’s cloudy today, that means the “weather” variable in my program at a particular time[1] takes on the value “cloudy”. Now, suppose your program and my program are exactly the same, except that somewhere in there I think a certain parameter has value 5 and you think it has value 0.3. Even though our programs differ in only that one little spot, we might still expect very different values of lots of variables during execution—in other words, we might have very different beliefs about lots of stuff in the world.
If your model and my model differ in that way, and we’re trying to discuss our different beliefs, then the obvious useful thing-to-do is figure out where that one-parameter difference is.
That’s a delta: one or a few relatively “small”/local differences in belief, which when propagated through our models account for most of the differences in our beliefs.
For those familiar with Pearl-style causal models: think of a delta as one or a few do() operations which suffice to make my model basically match somebody else’s model, or vice versa.
If the thing a discussion/debate is intended to establish is contingent on something, like a fact or theory, within your model of the world, then it would be a crux with respect to the debate. I assume that ‘cruxy’ refers to an attempt to quantify how much of the truth of the claim is dependent on that thing, i.e. to what extent it’s logically downstream of the piece of your world model whose status as a crux is under question.
Maybe the state of the clouds above a lake would to some extent be a crux relative to the question of what its volume will be tomorrow, but it’s still less cruxy than the flow—rate of a river which feeds into the lake in question. The river is upstream of the lake, whereas the clouds are above it, but both are logically upstream if it to some extent.
Because of the other comments, I don’t know how cruxy the existence of this comment is relative to whether metacelsus understands what the term means, but I have posted it in response to the ? reaction by Raemon to clarify what I meant.
I feel so happy that “what’s your crux?” / “is that cruxy” is common parlance on LW now, it is a meaningful improvement over the prior discourse. Thank you CFAR and whoever was part of the generation story of that.
As someone who hasn’t kept up much with the local jargon, what exactly does that mean?
“Is that cruxy” approximately means “is this proposition load bearing for your opinion on the broader topic we are discussing?”. I.e. if you are discussing whether god exists, and then in the process of that hit the question of whether historical Jesus was real, then one person can say “is this cruxy?” to mean “would you actually change your mind (or at least substantially update) on whether god exists if historical Jesus did in fact exist?”.
Thanks for explaining, I appreciate it!
See the crux tag. Duncan Sabien wrote the CFAR handbook’s double crux essay, etc.
Or maybe you’re more like johnswentworth and you think in terms of model deltas not cruxes:
https://www.lesswrong.com/posts/WLQspe83ZkiwBc2SR/double-crux
(and hover on the reactions on your comment)
Is it logically upstream of the areas of the answer to the question under debate, within your world-model ?
If the thing a discussion/debate is intended to establish is contingent on something, like a fact or theory, within your model of the world, then it would be a crux with respect to the debate. I assume that ‘cruxy’ refers to an attempt to quantify how much of the truth of the claim is dependent on that thing, i.e. to what extent it’s logically downstream of the piece of your world model whose status as a crux is under question.
Maybe the state of the clouds above a lake would to some extent be a crux relative to the question of what its volume will be tomorrow, but it’s still less cruxy than the flow—rate of a river which feeds into the lake in question. The river is upstream of the lake, whereas the clouds are above it, but both are logically upstream if it to some extent.
Because of the other comments, I don’t know how cruxy the existence of this comment is relative to whether metacelsus understands what the term means, but I have posted it in response to the ? reaction by Raemon to clarify what I meant.
“What’s your crux”≈”What is the thing [[1]] you’d have to change your view on what we’ve been discussing”.
Proposition, empirical fact, etc
Yeah that one specifically feels so useful and natural that I have some hope it might reach the wider world.
I heard “seems like [x] is a crux” at my STEM-focused workplace last week; I’m not aware of the speaker using LW.