本文探讨了决策理论中的两个核心概念：因果决策理论（CDT）和功能决策理论（FDT）。文章指出，CDT和FDT在评估反事实情境时采用了两种不同但内部一致的理论，并且这两种理论是相互矛盾的。CDT在进行反事实推断时，仅保留了世界模型中的因果结构；而FDT则在保留因果结构的基础上，还保留了所有与决策相关的从句依赖关系。这种根本性的差异导致了两种理论在某些情况下会得出截然相反的结论，并且CDT和FDT的代理人之间无法相互说服对方采纳其理论。文章还提到了人类自身也同时具备这两种决策直觉，并需要其他方式来调和这种内在的冲突。文中引用了相关文献，旨在澄清这两种理论的差异以及各自的直觉基础。

🧰 CDT与FDT是评估反事实情境的两种相互矛盾但内部自洽的理论。CDT在构建反事实时，仅保留世界模型中的因果结构；FDT则在保留因果结构的同时，也保留了所有与决策相关的从句依赖关系，这使得两者在处理某些问题时会产生截然不同的结果。

⚖️ CDT和FDT的代理人之间存在根本性的不兼容性。文章指出，一个CDT代理人无法被说服去采纳FDT的反事实评估方式，反之亦然。这意味着在决策过程中，一旦选择了其中一种理论，就很难被另一种理论所动摇。

💡 人类自身拥有两种决策直觉，需要通过其他方式调和。文章作者提到，人类天然就具备CDT和FDT的直觉，并且存在能够引发这些不同直觉的问题。如何在这两种相互冲突的直觉之间找到平衡和决策依据，是需要进一步探讨的议题。

📚 相关文献和术语解释。文章提及了功能决策理论（FDT）的原始论文以及在LessWrong（LW）社区中关于统一决策理论（UDT）的讨论，并建议从UDT的维基页面开始了解，以帮助理解这种逻辑风格，尽管作者本人也表示未能完全理解。

❓ 核心问题在于明确两种理论的差异和各自的直觉基础。作者希望明确CDT和FDT所指代的确切含义，以及各自理论所依赖的人类直觉是什么，并希望能找到能够激发这些不同直觉的具体问题。这表明对这两种决策理论的清晰阐释和区分是理解其核心冲突的关键。

Published on July 25, 2025 6:43 PM GMT

In this comment thread on the 2021 post “A Defense of Functional Decision Theory”, @So8res wrote:

...Also, just to be clear, you’re aware that these are two different internally-consistent but contradictory theories of how to evaluate counterfactuals? Like, we can be pretty confident that there’s no argument a CDT agent can hear that causes them to wish to adopt FDT counterfactuals, and vice versa. Humans come equipped with both intuitions (I can give you other problems that pump the other intuitions, if you’d like), and we have to find some other way to arbitrate the conflict.

Following up on my reply that I didn’t know what he was talking about, he recommended some reading:

The canonical explanatory text is the FDT paper (PDF warning) (that the OP is responding to a critique of, iirc), and there’s a bunch of literature on LW (maybe start at the wiki page on UDT? Hopefully we have one of those) exploring various intuitions. If you’re not familiar with this style of logic, I recommend starting there (ah look we do have a UDT wiki page). I might write up some fresh intuition pumps later, to try to improve the exposition. (We’ve sure got a lot of exposition if you dig through the archives, but I think there are still a bunch of gaps.)

I followed both of those links, and was not enlightened. The linked FDT paper had this bit:

In short, CDT and FDT both construct counterfactuals by performing a surgery on their world-model that breaks some correlations and preserves others, but where CDT agents preserve only causal structure in their hypotheticals, FDT agents preserve all decision-relevant subjunctive dependencies in theirs.

(This follows a rather technical section, which I have little confidence in having understood correctly.)

Has the dichotomy that @So8res refers to been clearly explained anywhere? If not—can anyone explain it now? The relevant questions are:

What are the “two different internally-consistent but contradictory theories of how to evaluate counterfactuals”?What are the intuitions for each (which humans come equipped with)?What problems pump those intuitions?

Discuss