Wolfgang Schwarz

Truth-conduciveness and rational priors

We Bayesians are sometimes bugged about ultimate priors: what probability function would suit a rational agent before the incorporation of any evidence? The question matters not because anyone cares about what someone should believe if they popped into existence in a state of ideal rationality and complete empirical ignorance. It matters because the answer also determines what conclusions rational agents should draw from their evidence at any later point in their life. Take the total evidence you have had up to now. Given this evidence, is it more likely that Obama won the 2008 election or that McCain won it? There are distributions of priors on which your evidence is a strong indicator that McCain won. Nevertheless, this doesn't seem like it's a rational conclusion to draw. So there must be something wrong with those priors.

Stalnaker on self-location

Here are some notes on Stalnaker's account of self-locating beliefs, in chapter 3 of Our Knowledge of the Internal World. I find the discussion there slightly intransparent, so I'll start with a presentation of what I take to be Stalnaker's account, but in my own words. This will lead to a few objections further down.

We start with extreme haecceitism. Every material object and every moment in time has, in addition to its normal, qualitative properties also a non-qualitative property, its 'haecceity', that distinguishes it from everything else. My haecceity belongs to me with metaphysical necessity, and could not belong to anyone else. Moreover, it is my only (non-trivial) essential property. (This is the 'extreme' part in extreme haecceitism.) In this world, I am a human being, but in other worlds, I am a cockatoo, or a poached egg. My haecceity is freely combinable with any qualitative property.

Stalnaker against internalism

Stalnaker holds a combination of views that seem independent to me, but closely connected to him. One is a kind of reductive naturalism about intentionality. On this view, the point of attributing beliefs and desires is to give a high-level characterisation of the subject's behavioural dispositions, their functional architecture and their causal relations to the environment. Another of Stalnaker's views is externalism about mental content. This says that intentional characterisations are relational: even when two subjects are perfect intrinsic and functional duplicates, they may still differ in their beliefs and desires, depending on what objects and properties they are causally related to.

Unique centers

Continuing the topic of the last post, suppose I'm certain that no-one else in the history of the universe ever had (or will have) exactly the experiences that I have now. Then I can 'translate' any centered proposition into an uncentered propositions in such a way that the translation is certain to preserve truth-values. For instance, "it is raining" gets translated into "it is raining at all times and places where someone has such-and-such experiences". In this case, one might think, purely centered information can never affect my uncentered beliefs. For purely centered information only distinguishes between multiple centers within a single world; but if no world has multiple possible centers, then there is nothing to learn from such information. (This line of reasoning is related to what Mike Titelbaum says in his forthcoming paper "The Relevance of Self-Locating Beliefs", though I don't think Mike would endorse the argument I present here.)

When centering matters

Darks clouds are gathering. Soon it will be raining. When it does, I will believe that it is raining. I do not yet believe that it is raining even though I do believe that my well-informed future self will believe that it is raining. I thereby violate the 'Principle of Reflection'. Once we allow for centered propositions that change their truth-value between times and places, Reflection, like its close cousin Conditioning, become very implausible norms of rationality.

OPP update

The OPP feed has been a bit bumpy recently because I made a few changes to the code. Things should be running smoothly again from today. The biggest changes are a bit of OCR to parse scanned documents (about 25% of all PDFs) and an improved algorithm to detect authors and co-authors. If you have contacted me about anything else: that has also been fixed.

How to change one's mind again

I've finally finished rewriting my paper on self-locating belief dynamics. Here is the new version. The presentation is quite different from before. In particular, I no longer use transition probabilities in modeling Cartesian agents, which allows me to be more specific about what these probabilities are. There's also a new section where I try to show that traditional arguments in support of conditioning turn into arguments for my revised rule when self-locating beliefs are considered.

Quantified counterfactuals, strict conditionals and escaping animals

Speaking of chapter six, Williamson here argues that the sentence

1) if an animal escaped from the zoo, it would be a monkey

is not adequately formalized as

1')

on the grounds that according to (1'), even the elephants are such that they would be monkeys if they escaped from the zoo. Williamson suggests that an adequate formalization might rather go like this:

Discoveries merely about concepts

Okay. Here are some thoughts on a talk Frank Jackson gave last week on Williamson on thought experiments.

The question is what Gettier discovered in his famous article. According to Frank, he revealed a fact about our concept 'knowledge': that it is not the same as our concept of justified true belief. According to Williamson, Gettier has revealed a fact about knowledge itself: that it is not justified true belief. A discovery merely about our concepts, Williamson says, "would show little of philosophical interest"; it would be "of significance primarily to theorists of concepts, not to epistemologists". For "the primary concern of epistemology is with the nature of knowledge, not with the nature of our concept of knowledge". (All of these are from p.206 of The Philosophy of Philosophy.) Frank disagrees. He thinks that results about the key concepts of a discipline are quite important to that discipline.

Online papers in philosophy feed

Long ago, I wrote a little script to automatize Brian Weatherson's (at the time) Online Papers in Philosophy blog. The script crawls the home pages of various philosophers and extracts author, title and abstract from every paper posted there. It then visits the pages again every other day or so to check for updates. This way, I'm currently tracking about 15000 papers from about 2000 pages.

Since the real OPP blog, maintained by Jonathan Ichikawa for the last few years, has caught a virus and is therefore not doing well right now, I've decided to dust off my script and make it available to the public. Then along came David Chalmers, who talked me into not making it public after all, but rather merging it into something even bigger that will hopefully go live very soonish. In the meantime, here is at least an RSS feed of my script, with daily updates of new papers it finds: OPP RSS.