Wolfgang Schwarz

Thesis

So here's the thesis (PDF, 250 pages, 1.7 MB and in German). I'm a little dissatisfied with the presentation: it shows that it was finished in a hurry. I will do some polishing before the obligatory publication, and I'd recommend not reading it through in its current state.

For the most part, the book is an overview of Lewis's philosophy, with an emphasis on metaphysics. I discuss Lewis's views on non-present times and non-actual worlds, on mathematics and properties, his physicalism and Humean Supervenience, and the basic framework of his philosophy of language. One aim of this is to ease the understanding of Lewis's positions by tracing out all the interconnections between his theories. More importantly, I try to show how the package can be broken up: that one can, for example, accept most of what Lewis says about language and laws of nature without accepting his modal realism and his doctrine of objective naturalness. There's also a rather lengthy discussion about methodology and the relationship between modal/metaphyical and analytical reduction.

I've posted most of the interesting bits in this weblog here while I was working on them, and I'll probably write two or three small papers (in English) about some of it in the coming months.

Blindsight in Ordinary People

In the latest issue of PNAS, there's an article on blindsight in ordinary people: The researchers induced local and temporary blindness by magnetically de-activating certain parts of brain area V1. When forced to choose, the subjects then often guessed correctly the direction or colour of a patch which they didn't consciously see.

(As usual, "consciously" is here functionally defined: what the subjects were missing is not some kind of non-functional, phenomenal consciousness, but a state with a certain functional role, leading in particular to utterances like "I saw a yellow patch". A case of truly phenomenal blindsight would be somebody who behaves in every way as if she consciously sees the patches, but who nevertheless doesn't see them consciously.)

Reliability

What does it take for something to be a perfectly reliable indicator of something else?

I'm not really familiar with discussions of reliability in epistemology, and I'd be grateful for pointers. Anyway, here is my own suggestion.

First, we need a mapping from (possible) states of the indicator to the indicated facts (or states or propositions). Let's say that the indicator displays that p, for short: I(p), if its state is mapped to p by that mapping. The mapping may be any old function (but the 'states' may not be any old Cambridge states): there is a good sense in which a clock that consistently runs 8 minutes fast is reliable; the tricky bit is only to read what it says, to figure out the mapping. This is the sense of "reliable" I'm interested in.

Changes II

Changes I

Lewis on meaning and fundamental O-terms

I thought after finishing my PhD thesis I would spend less time thinking and writing about Lewis for a change. But just then, Brian started his Lewis blog raising all kinds of interesting issues, like how to handle theoretical terms in multiply realised theories. I think Lewis's early suggestion to treat the terms as empty in those cases is much worse than he realised (than he realised even later, when he dropped the suggestion). I hope to say more about that later.

If it turns out that I'm Leverrier's wife

What would you say if it turns out that the watery stuff in our rivers and lakes doesn't actually consist of H2O, but of XYZ: would you say that water consists of H2O or XYZ?

What would you say if it turns out that you are Leverrier's wife living in 1845 and the heavenly body your husband calls "Neptune" is not a planet, but a spaceship: would you say that Neptune is a spaceship or a planet?

There's something odd about the second question.

I am disposed to assent to certain sentences under certain conditions, to "it's raining" if it's raining, etc. For each sentence, this determines a function from conditions -- sets of centered worlds -- to truth values. (If I am disposed to assent to S under condition C, that doesn't mean I assent to S in all C-worlds. I need only do so in the closest C-worlds. I am not disposed to assent to "it's raining" under the condition that it's raining and I am halluzinating that it doesn't rain.)

Some tricky counterfactuals

Sometimes, a counterfactual is true even though the consequent is false in the closest world where the antecedent is true:

1) If Hurricane Katrina hadn't hit the town with 200 km/h, completely destroying our house, we would be at home now, watching TV.

Presumably, at the closest worlds where Hurricane Katrina doesn't hit the town with 200 km/h and completely destroys the house, it hits the town a little faster or slower, still completely destroying the house. Even at the closest worlds where the hurricane doesn't completely destroy the house, it destroys it almost completely, still preventing the TV event.

Influence and Backwards Causation

About half a minute ago, I've poured tea into this cup. In a few seconds, I will take a sip. What if I had taken a sip a minute earlier? I wouldn't have taken a sip of tea from an empty cup: that is impossible. So there would have been tea in the cup a minute ago. How did it get there? Maybe I would have poured it in earlier. Or maybe it would have tunnelled directly from the pot into the cup. Or maybe the tea would have just materialized out of thin air. Some of these counterfactuals do not sound very plausible, but let's assume that for the kind of counterfactuals relevant to causation, they are all equally good so that there is no fact of the matter about how the tea got into the cup at the closest world where I take the sip a minute earlier: it does so differently at different worlds that are equally close. (See Lewis, "Counterfactual Dependence and Time's Arrow" for the standards of evaluating such counterfactuals, and "Are we free to break the laws?" for the indeterminacy of divergence miracles.)

Are logical truths true?

1. Hesperus is identical to Phosophorus.
2. By modal logic, .
3. Therefore, Hesperus is necessarily identical to Phosphorus.

1. Sometimes, one is obliged to do things that are not allowed.
2. By deontic logic, .
3. Therefore, sometimes one is obliged to things that are both allowed and not allowed.

1. Necessarily, if the moon essentially consists of green cheese, then it actually consists of green cheese.
2. By provability logic, .
3. Therefore, the moon essentially consists of green cheese.

1. It is now 20 seconds past 19:00 hours.
2. It is now 30 seconds past 19:00 hours.
3. If it is now 30 seconds past 19:00 hours, it is not now 20 seconds past 19:00 hours.
4. By propositional logic, .
5. Therefore, the moon is made of green cheese.

What's wrong with these arguments? They are invalid: their premises are true, their conclusion false. In each case, the fallacy is to assume that a principle valid in some formal system is also valid when translated into English.