TEACH SEM2A8.CONCEPTS Aaron Sloman Nov 1995 Re-formatted 12 Jun 2006 SOME PROBLEMS CONCERNING SENSE AND NONSENSE =========================================== Below you will find some questions concerned with how we understand words, or make sense of words. Put another way: the questions are about the concepts we use in our thinking, perceiving, reasoning, deciding, etc. You may find that you have theories about these topics which you did not realise you had. In the course of answering the questions you may change your mind. Try to *think* about the problems. Even if you've read something relevant, don't just write down what you've read: write down what you think. Write your answers down with wide margins so that you can go back and write down afterthoughts, corrections, etc. At the end, you may find it useful to try to organise your ideas into an essay. Don't be worried if you find the problems hard: even if you do, try to write something down in answer to each question, as a way of getting started. If you find the questions easy to answer, that probably means you should think a little more. Several of the questions are inter-related. Later questions may help you to extend or criticise your answers to earlier questions. So it may be a good idea not to read beyond a question until you've tried thinking or writing about it. Many of the questions below are about words. This may mislead you into thinking they are MERELY about words. Words are among the most important of our thinking tools. (Why?) Furthermore, by analysing some of the words we use we can begin to understand some of the problems about how people learn, how they communicate, how they represent reality -- in short, what they are. And that means you too! Some questions to think about, talk about, write about ------------------------------------------------------ (1) Can a person who has been blind from birth understand words concerned with sight, like 'blue', 'colour', 'see'? What about 'square', 'freckle', 'pretty'? Is there a similar problem about a person who has been deaf from birth? Try not merely to give your answers to these questions, but also to give your reasons. Do you have evidence for your views? Could you produce arguments to try to convince someone who disagreed with you? (There are sure to be people who disagree with you!) (2) What is 'learning from experience'? What does it mean to say that you've learnt a word from experience? Do we learn colour words from experience? Suppose you point to something blue and say "blue": will that teach a person what the word "blue" means? If the object is square and heavy, might he think that "blue" really means "square", or "heavy", or "square and heavy", or "blue and square and heavy"? What other misunderstandings can occur when you try to teach the meaning of a word by giving someone experiences of the things it describes? Can the misunderstandings be eliminated? (3) Is there any other way of learning the words mentioned above? What about words like "shape", "number", "true", "not"? (4) What does a person need to know in advance in order that he can learn a word (e.g. "arch") as a result of your pointing to examples? (5) Can we ever understand words or phrases referring to things we have never experienced? Write down some words or phrases which refer to things you have never experienced, and discuss the extent to which you think you might understand them. (6) Why have you never experienced those things? Are there some things which cannot be experienced, like the atoms, an infinitely long line, the beginning of time, democracy, the meaning of "or"? Can you think of anything else? (7) How can one tell that a child understands a word, like "blue"? If the child points at something blue and says "blue", how can you tell which aspect of the thing he is referring to? Is your problem of understanding the child any different from the child's problem of understanding you? (8) What does "understand" mean? How could you decide whether a blind person understood 'blue' or did not? How could you decide whether a deaf person understood 'tune', 'high-pitched' or not? How can you decide in the case of someone who isn't blind or deaf? (9) When I say something looks square and when I say it feels square, am I using the word "square" with the same meaning, or with two different meanings? Are there two kinds of squareness, or one kind perceivable with different senses? How can this sort of question be answered? (10) If someone claimed to be able to perceive aspects of physical objects or human minds that others couldn't, because he had an extra-sensory ability, how could you decide whether he was a fraud or not? Would any sort of experiment convince you? Suppose he could distinguish objects which you found indistinguishable? How could you test this? (11) Could you use a similar test to convince a blind person you can see things? (12) Scientists often talk about things which they cannot see, hear, smell, taste or feel, like atoms, genes, cosmic radiation. Write down some more examples if you can. Do you think anyone really understands any of these things? How can scientists tell whether they are communicating successfully? Can they? (13) Do you understand any of the following expressions? "atom", "electron", "electricity", "war", "population explosion", "genes", "starvation", "totalitarianism", "moral decline", "infinitely long lines", "magnetic force", "ancient Greece", "The South Pole", "the number 26 million", "economic pressures", "our culture", "the spirit of an age". Are these all things you have experienced? If not, does that mean you cannot understand anyone who talks about them? (14) Is your position in relation to these words anything like the blind person's position in relation to colour words? If not, what's the difference? (15) Try to make a list of words or phrases referring to things you have never experienced, but which you understand (including examples given above, if appropriate). Then try to write down, for some of them, an explanation of how you came to understand them, and how you might decide whether somebody else understood them in the same way as you. Is your problem in understanding these things any different from the problem of the person who has been blind or deaf from birth? (16) Have you changed your mind about anything you wrote in answer to question 1. If so, why? (17) A "concept empiricist" is (roughly) one who thinks that all our concepts have to be derived from experience of examples of those concepts. Are you a concept empiricist? Look at your answer to 1. (Many scientists, e.g. "behaviourist" psychologists, have been influenced by concept empiricism.) "Knowledge empiricism" is a different view - that all *knowledge*, or, more precisely, knowledge about which propositions are true and which false, is derived from experience. This is the view that there is no knowledge which is "a priori". Usually people inclined to this view adopt the less extreme position that there is some a priori (non-empirical) knowledge, but it is all 'analytic'. Concept empiricism is concerned with where concepts, the building blocks of propositions, come from. Knowledge empiricism is concerned with how we discover the truth-values of complete propositions. (18) Does concept empiricism entail knowledge empiricism? (19) Does knowledge empiricism entail concept empiricism? (20) Under what conditions, if any, would you say that a machine's behaviour was convincing evidence that it understood English words, like 'blue', 'heavy', 'dog'; or any other words? Could any *behaviour* of a congenitally blind person persuade you that he understood colour words in the same sense as you did? E.g., suppose you and the blind person both had hoods over your heads, so that neither of you could see anything, and suppose a sighted interrogator could not tell which of you was temporarily blind and which permanently. Would that prove that the really blind person understood colour words as well as you did? (21) How can experiences teach you a concept? Suppose I wanted to teach you the concept "throw": would it do to show you lots of examples of someone throwing something? Why wouldn't you assume that "throw" meant "person", or "moving object", or "propel", or "two things move apart", etc.? What kinds of software could give a computer the ability to learn these things from being shown examples? (Incidentally, what is the difference between "throw" and "push" and "propel" and "move", and ..... ? Try to analyse the similarities and differences between these and other verbs concerned with motion. How do you think children manage to learn such complex concepts?) (22) What is it to grasp, or understand, a concept, like "near", or "colour", or "blue"? Would a being which did not already have some concepts be capable of having experiences? Kant argued that this would be impossible, in the Introduction to his Critique of Pure Reason, (reprinted in Edwards and Pap). Is it possible that people are born with some concepts? (23) Could I teach you the concept "between" by showing you some examples of instances of "x is between y and z"? Would I have to show you examples for all possible sorts of "between-ness" - between in size, in position, in colour, in pitch, in level of understanding of mathematics, in magnitude of electric current. What about one electron's orbit being between two others? Do all these uses of "between" have the same meaning? How can the very same meaning be exemplified in very different experiences? Yet if the meanings are different, why should we use the same word? How come people agree on how to extend the word to a new context? (24) David Hume argued that there was no way the concept "cause" could be learnt from experience. Everytime you are presented with an example of A causing B, all you actually experience is A preceding B, with perhaps other relations like proximity, physical connection via strings, etc. If we can't experience the causal connection how can we attach any meaning to the word "cause"? Is there any reason to believe we attach the same meaning to it? If not is our whole legal system based on false assumptions? (Kant thought "cause" was an a priori concept - one presupposed by experience, not derived from experience.) (25) If we were born with no concepts at all, could we begin to learn? How? What sorts of learning mechanisms would suffice to explain all the kinds of learning that infants do? (26) If you wish to write an essay, on some topic arising out of these questions, you could choose as a title, for example, "Sense and Nonsense", or "The limits of Intelligibility", or "What is it to understand a word?" or "How can one understand talk of what one has never or could never experience?" You could try writing a first draft without any special reading. Relevant Reading ---------------- This is just a small subset of a huge amount of relevant literature. Work in AI on concept formation and learning complements this. One of the most comprehensive discussions is the paper by C.G. Hempel 'Problems and changes in the empiricist criterion of meaning', originally published in Revue Internationalede Philosophie, Vol. 4 (1950). Part of it is re-printed in Nagel and Brandt (see below). Complete versions are in the collections edited by A.J. Ayer and L. Linsky (see below). J. Hospers, Introduction to Philosophical Analysis, (second edition). Sections 5, 14, 15. P. Edwards and A.Pap (eds), A Modern Introduction to Philosophy, Part VIII - 'Meaning Verification Metaphysics'. E. Nagel and R.B. Brand (eds), Meaning and Knowledge, Chapter 1 part A. A.J. Ayer (ed), Logical Positivism, Chapters 2 to 5. L .Linksy (ed) Semantics and the Philosophy of Language. Paper by Hempel. If you'd like to discuss the relevance of work on concept learning in Artificial Intelligence you might look at the descriptions of Winston's concept learning program in one of the following - the last being the fullest account: M. Boden Artificial Intelligence and Natural Man, 2nd Edition P.H. Winston, Artificial Intelligence 3rd Edition P.H. Winston (ed), The Psychology of Computer Vision. There is other work on concept formation in AI, described in recent text books. --- $poplocal/local/teach/sem2a8.concepts --- The University of Birmingham 1995. --------------------------------