Wed 12th March 12:30-14:00
‘Epistemic and Inferential Consistency in Knowledge-Based Systems’
One way to understand the knowledge-based systems approach to AI is as the attempt to give an artificial agent knowledge (or give it the ability to act like a human that has that knowledge) by putting linguaform representations of that knowledge into the agent’s database (its knowledge base). The agent can then add to its knowledge base by applying rules of inference to the sentences in it. An important desideratum for this process is that only true sentences are added (else they cannot be knowledge). Since typical rules of inference would allow the addition of any sentences, including false ones, to an inconsistent database, care must be taken to ensure that knowledge bases are consistent. Much effort has been expended on devising tractable ways to do this (e.g., truth maintenance systems, assumption-based truth maintenance systems, partitioned paraconsistent knowledge bases that are locally consistent but may be globally inconsistent, etc.) I argue that for certain kinds of knowledge representation languages (autoepistemic logics), a further constraint, which I call epistemic consistency, must be met. I argue for the need to check for epistemic consistency despite the fact that, unlike for consistency simpliciter, failing to meet this constraint is not a logical possibility. The most basic form of checking that this constraint is met is to ensure that there are no sentences in an agent’s knowledge base that constitute what Sorensen has called an epistemic blindspot for that agent (e.g., “It is raining, but Hal doesn’t know it”, for the agent Hal). This constraint must be maintained both when initialising the knowledge base, and when applying rules of inference, a fact which requires generalising from Sorensen’s notion of an epistemic blindspot to the concept of epistemic blindspot sets (a move that is independently motivated in applying Sorensen’s surprise examination paradox solution to the strengthened paradox of the toxin). In addition, and along similar lines, I argue that another form of consistency, which I call inferential consistency, must be maintained. Inferential consistency does not involve epistemically problematic sentences, but rather epistemically problematic inferences, such as ones concerning the number of inferences one has made. I consider one way of dealing with such cases, which has the alarming consequence of rendering all rules of inference strictly invalid. Specifically, I argue that the validity of a rule of inference can only be retained if a semantic restriction (that of excluding reference to the inference process itself) is placed on the sentences over which it can operate.
Fellow Sackler member Jim Parkinson brought to my attention the fact that this year’s Flame Challenge – explaining science to 11-year-olds in less than 300 words – is on the topic “What is Color?”. I decided to take up the challenge; here’s my entry (299 words!):
The question “what is color?” is tricky. Understood one way, it hardly needs answering for people with normal vision, who have no problem learning how to use the word “color” and what the names for different colors are: color is just part of the way that things look. But that answer would be of little use to a blind person, since for them objects don’t “look” any way at all. Science should try to explain things for everyone, so here’s an explanation of color that works for all people, sighted or blind.Light is a collection of extremely small particles called photons. A photon might begin its journey at a lamp, bounce off an object (such as a book), and end its journey by being absorbed by one of the cells that line the back wall inside your eye. Photons wiggle while moving – some wiggle slowly, some quickly.The color of an object is the mixture of wiggle speeds of photons the object gives off in normal light.Sighted people can see an object’s color because the way a photon affects their eye cells depends on its wiggle speed. For example, if your eye absorbs a slow wiggling photon, you see red; a fast wiggling photon, you see blue. Mixtures of wiggle speeds have a mixture of effects on your eye cells, letting you see a mixture of colors. Something colored white gives off photons of all wiggle speeds.If you shine red light on a white ball it looks red, but its actual color is still white because if it were in normal light it would give off photons of all wiggle speeds. Similarly, a blue book in the dark is still blue because it would still give off fast wiggling photons were it in normal light.
Working on thesis.
Working on Joint Session talk. Thought my subject – panpsychism and the composition problem – would be a welcome change from natural kinds and downward causation, but it turns out that deproblematising composition and adding the idea of the mind being composed of multiple virtual machines is a good way of arguing for non-reductive, downwardly causal mental properties.
Working on talk for E-int and Joint Session.
Went to 1st person approach conference in Berkeley – changed plan and gave a response to Susan Stewart’s criticism of synthetic phenomenology work.
Gave talk last week to philosophy faculty research progress meeting.
Going to Sweden on Monday till August.
Supervising MSc student – implementing web browsing advisor built on architecture inspired by Bernard Baars global workspace theory.
Preparing for presentation & working on thesis.
1 – The philosophy of mind reading group (see http://www.ifl.pt/index.php?id1=3&id2=8) had a meeting on a draft chapter of my book: Cognitive Technologies in Everyday Life: Tools for Thinking and Feeling. It generated some interesting discussion and it was very nice for me after all the time I’ve put into this.
2 – I’ve started organizing a research in progress group modelled on … you’ve guessed it E-I which will hopefully meet for the first time next week.
3 – Trying to finish a review for JCS of The Crucible of Consciousness by Zoltan Torey which is supposed to be in Friday.
Working on Joint Session talk.
- Wrote paper with Blay for “What Makes Us Moral?” conference in Amsterdam at month’s end and submitted it to the conference website. Presented the paper at a seminar here for last-minute feedback before submission.
- Re-wrote Chapter 5 of my thesis “The Limits of Concepts and Conceptual Abilities” into a standalone paper for a course I’m attending of the SweCog National Research School in Cognitive Science. Planning to submit it somewhere by month’s end.
- Doctoral thesis went lost in the (registered) post. So far neither Sweden nor the UK want to claim responsibility. Annoying as this may complicate my pay-grade change to postdoc status (seriously). Did I mention that the first time the bookbinders bound my thesis, they got my name wrong?
Apologies for the delay.
- Collected my bound thesis from the bookbinders on Monday and posted it to Sussex: pretty much the last thing I have to do before I officially have earned my degree!
- Finished a first re-write of the paper I presented at Toward a Science of Consciousness – Stockholm, hoping to submit in the next few weeks (on the limits of concepts and conceptual abilities).
- Engaging in some email discussions with Blay and a philosopher here in Lund about compatibilism.
- Assisting Göran Sonesson with comments on a paper he is submitting, on the ability of chimpanzees to interpret different semiotic resources.
- Making painfully slow progress on the paper I need to write (so I can present!) at the What Makes Us Moral? conference in Amsterdam later this month.
- Trying to write a paper on Kirsh & Maglio’s epistemic action/pragmatic action distinction.
- Also Bob Chad sent his apologies for non-attendance today.
- Didn’t get the job in Norway.
- Finished my thesis corrections and sent them (unofficially) to the examiners. Still waiting on the formal notification from the university of the examiners’ recommendation / official list of and timetable for corrections, which I gather is now in the post.
- Invited for talk in Skövde for a psychology course on cognitive neuroscience (not exactly my area, I admit).
- Need to prepare talks for Toward a Science of Consciousness – Stockholm and the Nordic Association for Semiotic Studies, both at the start of May.
- Abstract accepted for poster at ASSC/Kyoto, but the expense doesn’t justify attending. Likewise I had a paper accepted for a short presentation at the Scandanavian Association for AI but ran out of time to re-format it to their needs, so again won’t be attending.
- Last week I attended a course on concepts hosted by SweCog (the National Research School in Cognitive Science). It was interesting, to say the least, to see my thesis subject matter presented back to me in a very different format by people from very different backgrounds to my own.
- This week I am proofreading like mad: in particular, Paulina Lindström’s doctoral thesis investigating mathematical problem solving and the precise moment when subjects understand the problem.
- I have finally, I think!, seen the last of the back-and-forth questions about my extended mind paper, which will be appearing in Teorema in, I think, May.
- I need to get started on my half-dozen thesis corrections. They shouldn’t take long to crank out; I just haven’t had any time.
As always, there are various things I should be working on getting published, and I am behind on my reading. Hope to be back for a visit sometime next term!