# Func­tional De­ci­sion Theory

TagLast edit: 17 Nov 2022 5:31 UTC by

Functional Decision Theory is a decision theory described by Eliezer Yudkowsky and Nate Soares which says that agents should treat one’s decision as the output of a ﬁxed mathematical function that answers the question, “Which output of this very function would yield the best outcome?”. It is a replacement of Timeless Decision Theory, and it outperforms other decision theories such as Causal Decision Theory (CDT) and Evidential Decision Theory (EDT). For example, it does better than CDT on Newcomb’s Problem, better than EDT on the smoking lesion problem, and better than both in Parﬁt’s hitchhiker problem.

In Newcomb’s Problem, an FDT agent reasons that Omega must have used some kind of model of her decision procedure in order to make an accurate prediction of her behavior. Omega’s model and the agent are therefore both calculating the same function (the agent’s decision procedure): they are subjunctively dependent on that function. Given perfect prediction by Omega, there are therefore only two outcomes in Newcomb’s Problem: either the agent one-boxes and Omega predicted it (because its model also one-boxed), or the agent two-boxes and Omega predicted that. Because one-boxing then results in a million and two-boxing only in a thousand dollars, the FDT agent one-boxes.

# Func­tional De­ci­sion The­ory: A New The­ory of In­stru­men­tal Rationality

20 Oct 2017 8:09 UTC
16 points
(arxiv.org)

# Let’s Dis­cuss Func­tional De­ci­sion Theory

23 Jul 2018 7:24 UTC
29 points

# De­con­fus­ing Log­i­cal Counterfactuals

30 Jan 2019 15:13 UTC
27 points

# A Cri­tique of Func­tional De­ci­sion Theory

13 Sep 2019 19:23 UTC
82 points

# Dis­solv­ing Con­fu­sion around Func­tional De­ci­sion Theory

5 Jan 2020 6:38 UTC
31 points

# AXRP Epi­sode 5 - In­fra-Bayesi­anism with Vanessa Kosoy

10 Mar 2021 4:30 UTC
33 points

# Violent Un­rav­el­ing: Suici­dal Majoritarianism

29 Jul 2021 9:29 UTC
6 points

# MIRI/​OP ex­change about de­ci­sion theory

25 Aug 2021 22:44 UTC
49 points

# A Defense of Func­tional De­ci­sion Theory

12 Nov 2021 20:59 UTC
23 points

# A Re­ac­tion to Wolf­gang Sch­warz’s “On Func­tional De­ci­sion The­ory”

5 Jan 2022 9:00 UTC
5 points

# Cri­tiquing Scasper’s Defi­ni­tion of Sub­junc­tive Dependence

10 Jan 2022 16:22 UTC
6 points

# Defend­ing Func­tional De­ci­sion Theory

8 Feb 2022 14:58 UTC
4 points

# An In­tu­itive In­tro­duc­tion to Func­tional De­ci­sion Theory

7 Mar 2022 16:07 UTC
21 points

# Alex Tabar­rok ad­vo­cates for crowd­fund­ing sys­tems with *Re­fund Bonuses*. I think this might be a nat­u­ral oc­cur­rence of a money pump against Causal De­ci­sion The­ory pledgers

14 Mar 2022 7:27 UTC
16 points
(marginalrevolution.com)

# No, EDT Did Not Get It Right All Along: Why the Coin Flip Creation Prob­lem Is Irrelevant

30 Mar 2022 18:41 UTC
6 points

# [Question] What does Func­tional De­ci­sion The­ory say to do in im­perfect New­comb situ­a­tions?

7 May 2022 22:26 UTC
4 points

# [Question] Al­gorith­mic for­mal­iza­tion of FDT?

8 May 2022 1:36 UTC
12 points

# New­comb­ness of the Din­ing Philoso­phers Problem

6 Aug 2022 21:58 UTC
10 points

# Log­i­cal coun­ter­fac­tu­als are brit­tle; use conditionals

15 Sep 2022 8:55 UTC
20 points

# FDT is not di­rectly com­pa­rable to CDT and EDT

29 Sep 2022 14:42 UTC
29 points

# You’re Not One “You”—How De­ci­sion The­o­ries Are Talk­ing Past Each Other

9 Jan 2023 1:21 UTC
26 points

# Quan­tum Suicide, De­ci­sion The­ory, and The Multiverse

22 Jan 2023 8:44 UTC
4 points