Jessica Taylor

Jessica Taylor. CS undergrad and Master's at Stanford; former research fellow at MIRI.

I work on decision theory, social epistemology, strategy, naturalized agency, mathematical foundations, decentralized networking systems and applications, theory of mind, and functional programming languages.


Modeling naturalized decision problems in linear logic

CDT and EDT have known problems on 5 and 10. TDT/UDT are insufficiently formalized, and seem like they might rely on known-to-be-unfomalizable logical counterfactuals.

So 5 and 10 isn't trivial even without spurious counterfactuals.

What does this add over modal UDT?

  • No requirement to do infinite proof search
  • More elegant handling of multi-step decision problems
  • Also works on problems where the agent doesn't know its source code (of course, this prevents logical dependencies due to source code from being taken into account)

Philosophically, it works as a nice derivation of similar conclusions to modal UDT. The modal UDT algorithm doesn't by itself seem entirely well-motivated; why would material implication be what to search for? On the other hand, every step in the linear logic derivation is quite natural, building action into the logic, and encoding facts about what the agent can be assured of upon taking different actions. This makes it easier to think clearly about what the solution says about counterfactuals, e.g. in a section of this post.

Topological metaphysics: relating point-set topology and locale theory

Reals are still defined as sets of (a, b) rational intervals. The locale contains countable unions of these, but all these are determined by which (a, b) intervals contain the real number.

Topological metaphysics: relating point-set topology and locale theory

Good point; I've changed the wording to make it clear that the rational-delimited open intervals are the basis, not all the locale elements. Luckily, points can be defined as sets of basis elements containing them, since all other properties follow. (Making the locale itself countable requires weakening the definition by making the sets to form unions over countable, e.g. by requiring them to be recursively enumerable)

Motivating Abstraction-First Decision Theory

I've also been thinking about the application of agency abstractions to decision theory, from a somewhat different angle.

It seems like what you're doing is considering relations between high-level third-person abstractions and low-level third-person abstractions. In contrast, I'm primarily considering relations between high-level first-person abstractions and low-level first-person abstractions.

The VNM abstraction itself assumes that "you" are deciding between different options, each of which has different (stochastic) consequences; thus, it is inherently first-personal. (Applying it to some other agent requires conjecturing things about that agent's first-person perspective: the consequences it expects from different actions)

In general, conditions of rationality are first-personal, in the sense that they tell a given perspective what they must believe in order to be consistent.

The determinism vs. free will paradox comes about when trying to determine when a VNM-like choice abstraction is valid of a third-personal physical world.

My present view of physics is that it is also first-personal, in the sense that:

  1. If physical entities are considered perceptible, then there is an assumed relation between them and first-personal observations.
  2. If physical entities are causal in a Pearlian sense, then there is an assumed relation between them and metaphysically-real interventions, which are produced through first-personal actions.

Decision theory problems, considered linguistically, are also first-personal. In the five and ten problem, things are said about "you" being in a given room, choosing between two items on "the" table, presumably the one in front of "you". If the ability to choose different dollar bills is, linguistically, considered a part of the decision problem, then the decision problem already contains in it a first-personal VNM-like choice abstraction.

The naturalization problem is to show how such high-level, first-personal decision theory problems could be compatible with physics. Such naturalization is hard, perhaps impossible, if physics is assumed to be third-personal, but may be possible if physics is assumed to be first-personal.

Subjective implication decision theory in critical agentialism

Looking back on this, it does seem quite similar to EDT. I'm actually, at this point, not clear on how EDT and TDT differ, except in that EDT has potential problems in cases where it's sure about its own action. I'll change the text so it notes the similarity to EDT.

On XOR blackmail, SIDT will indeed pay up.

Two Alternatives to Logical Counterfactuals

Yes, it's about no backwards assumption. Linear has lots of meanings, I'm not concerned about this getting confused with linear algebra, but you can suggest a better term if you have one.

Two Alternatives to Logical Counterfactuals

Basically, the assumption that you're participating in a POMDP. The idea is that there's some hidden state that your actions interact with in a temporally linear fashion (i.e. action 1 affects state 2), such that your late actions can't affect early states/observations.

Two Alternatives to Logical Counterfactuals

The way you are using it doesn’t necessarily imply real control, it may be imaginary control.

I'm discussing a hypothetical agent who believes itself to have control. So its beliefs include "I have free will". Its belief isn't "I believe that I have free will".

It’s a “para-consistent material conditional” by which I mean the algorithm is limited in such a way as to prevent this explosion.

Yes, that makes sense.

However, were you flowing this all the way back in time?

Yes (see thread with Abram Demski).

What do you mean by dualistic?

Already factorized as an agent interacting with an environment.

Two Alternatives to Logical Counterfactuals

Secondly, “free will” is such a loaded word that using it in a non-standard fashion simply obscures and confuses the discussion.

Wikipedia says "Free will is the ability to choose between different possible courses of action unimpeded." SEP says "The term “free will” has emerged over the past two millennia as the canonical designator for a significant kind of control over one’s actions." So my usage seems pretty standard.

For example, recently I’ve been arguing in favour of what counts as a valid counterfactual being at least partially a matter of social convention.

All word definitions are determined in large part by social convention. The question is whether the social convention corresponds to a definition (e.g. with truth conditions) or not. If it does, then the social convention is realist, if not, it's nonrealist (perhaps emotivist, etc).

Material conditions only provide the outcome when we have a consistent counterfactual.

Not necessarily. An agent may be uncertain over its own action, and thus have uncertainty about material conditionals involving its action. The "possible worlds" represented by this uncertainty may be logically inconsistent, in ways the agent can't determine before making the decision.

Proof-based UDT doesn’t quite use material conditionals, it uses a paraconsistent version of them instead.

I don't understand this? I thought it searched for proofs of the form "if I take this action, then I get at least this much utility", which is a material conditional.

So, to imagine counterfactually taking action Y we replace the agent doing X with another agent doing Y and flow causation both forwards and backwards.

Policy-dependent source code does this; one's source code depends on one's policy.

I guess from a philosophical perspective it makes sense to first consider whether policy-dependent source code makes sense and then if it does further ask whether UDT makes sense.

I think UDT makes sense in "dualistic" decision problems that are already factorized as "this policy leads to these consequences". Extending it to a nondualist case brings up difficulties, including the free will / determinism issue. Policy-dependent source code is a way of interpreting UDT in a setting with deterministic, knowable physics.

Two Alternatives to Logical Counterfactuals

I think it's worth examining more closely what it means to be "not a pure optimizer". Formally, a VNM utility function is a rationalization of a coherent policy. Say that you have some idea about what your utility function is, U. Suppose you then decide to follow a policy that does not maximize U. Logically, it follows that U is not really your utility function; either your policy doesn't coherently maximize any utility function, or it maximizes some other utility function. (Because the utility function is, by definition, a rationalization of the policy)

Failing to disambiguate these two notions of "the agent's utility function" is a map-territory error.

Decision theories require, as input, a utility function to maximize, and output a policy. If a decision theory is adopted by an agent who is using it to determine their policy (rather than already knowing their policy), then they are operating on some preliminary idea about what their utility function is. Their "actual" utility function is dependent on their policy; it need not match up with their idea.

So, it is very much possible for an agent who is operating on an idea U of their utility function, to evaluate counterfactuals in which their true behavioral utility function is not U. Indeed, this is implied by the fact that utility functions are rationalizations of policies.

Let's look at the "turn left/right" example. The agent is operating on a utility function idea U, which is higher the more the agent turns left. When they evaluate the policy of turning "right" on the 10th time, they must conclude that, in this hypothetical, either (a) "right" maximizes U, (b) they are maximizing some utility function other than U, or (c) they aren't a maximizer at all.

The logical counterfactual framework says the answer is (a): that the fixed computation of U-maximization results in turning right, not left. But, this is actually the weirdest of the three worlds. It is hard to imagine ways that "right" maximizes U, whereas it is easy to imagine that the agent is maximizing a utility function other than U, or is not a maximizer.

Yes, the (b) and (c) worlds may be weird in a problematic way. However, it is hard to imagine these being nearly as weird as (a).

One way they could be weird is that an agent having a complex utility function is likely to have been produced by a different process than an agent with a simple utility function. So the more weird exceptional decisions you make, the greater the evidence is that you were produced by the sort of process that produces complex utility functions.

This is pretty similar to the smoking lesion problem, then. I expect that policy-dependent source code will have a lot in common with EDT, as they both consider "what sort of agent I am" to be a consequence of one's policy. (However, as you've pointed out, there are important complications with the framing of the smoking lesion problem)

I think further disambiguation on this could benefit from re-analyzing the smoking lesion problem (or a similar problem), but I'm not sure if I have the right set of concepts for this yet.

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