How do we know we are not a computer program? In other words, some kind of video game? I know of the the brain in a vat argument but why suppose we have a brain at all? What if our "mind" is a computer only running a "human program" or some such thing? What if all sensation is just data in a computer and all "WE" are is just data in a computer? Any problems with this argument?

It's not obvious what the argument is here. Are we trying to argue that we actually are just avatars in a computer simulation? If so, then the argument seems pretty weak. Are we trying to argue that we don't know that we're not avatars in a computer simulation? Then., again, one wants to know what the argument actually is. It seems to be something like: We can't absolutely rule out that we're not avatars, etc, etc. And if so, then, yes, I agree that Putnam's brain-in-a-vat argument is actually pretty hopeless. But my own view, for what it's worth, is that the BIV argument doesn't actually have anything to do with skepticism. (I think it has to do with metaphysical realism, a very different topic.) But the deeper question, I think, is whether knowing that p actually requires being able to rule out the bare possibility that not- p , and not everyone would agree that it does, especially where skeptical scenarios are concerned. Have a peek, for instance, at Jim Pryor's paper "The Skeptic and the...

Abigail and Brittany Hensel, born 1990, midwest USA A very rare, dicephalus pair, they have separate heads and necks, but share one torso and a pair of legs. Each has her own heart and stomach, and controls the limbs and feels sensation exclusively on her own side. They share three lungs and, below the waist, a single set of organs. Physically they move as one, in perfect co-ordination. Mentally they are independent, with different preferences and abilities. Their parents are opposed to separation, which would be highly dangerous. Even if successful, the girls would be left severely disabled, and unable to enjoy walking, running, swimming and bike riding which, together, they can do easily. I am a Cartesian Dualist - I think! Does this situation above not solve the Mind/Body, Mind/Brain problem?

I think I'm confused. The two girls have two brains---one each. So I don't see any threat here to mind--brain identity. There is something philosophically interesting about the fact that the girls, together, can ride a bike, etc, using their shared torso, etc, and I'd be interested to hear what people who work on the body would have to say about them. One would really need to know a lot more about them---about what their ability to control "their" legs are like, etc. But I don't see any threat here either to dualism---though dualism does have its own share of problems.

Is mathematics somehow "scientific"? Let me explain. There is a sense in which scientific theories are ad hoc. We have a set of relevant observations, and we try to formulate a theory which (1) accounts for all of them and (2) is parsimonious. A theory here is just an explanatory principle tailored to capture the data we want. What we don't do is deduce scientific theories from foundational principles. Axioms in math often strike me as very much like this. The only difference is that the "data" or "observations" of interest here are our intuitions about mathematics (e.g., that A+B=B+A). When I look at the axioms of ZF set theory (for example), I don't see where they're supposed to be coming from; rather, they're just one ad hoc way of justifying propositions we feel must be justified. Isn't there something weird, though, about tweaking one's axioms to fit one's intuitions?

There are different ways of approaching axiomatization. One is more "top down". You have a pretty good idea what the truths are about a particular subject matter, and the problem is to find some reasonably managable set of principles from which those truths all follow. Axiomatizations of logic itself might be so construed. It's arguable that the fundamental notion here is really validity, the semantic notion, defined in terms of interpretations and the like, and then the problem is to find a set of axioms from which all the valid formulae will be derivable. Whether the axioms have some intuitive basis may be neither here nor there. Of course, that needn't be the only way of looking at the matter, and it doens't seem terribly plausible in the case of set theory, especially after one's naivete has been shattered by the paradoxes. Here more of a "bottom up" perspective might seem appropriate: One might think that the axioms of set theory ought in fact to have some kind of intuitive basis. And, as it...

Once capital punishment was right and fornication was wrong. Now the reverse seems generally true. Is there any way that philosophy can prepare us for future alterations in our values, perhaps by indicating where they are likely to arise?

It is not at all obvious that captial punishment used to be morally permissible. What is obvious is that most people, or some powerful people, or something along those lines thought it was morally permissible (that is, "right" or "OK"). It may well be that it was always morally impermissible (that is, "wrong"), but people didn't realize this. That would certainly be my view. There's nothing peculiar about what I'm suggesting. People used to think the earth was at the center of the universe. It wasn't. They were wrong. People used to think it was OK to leave babies on the sides of mountains to die in the noonday sun. They too were wrong. Maybe the same goes for capital punishment. And even sex outside of marriage. So philosophy can at least contribute that sort of clarification. And maybe a bit more: By examining our presumptions carefully, perhaps philosophy can help us realize that what we think, even what we really, firmly believe, isn't right, after all.

Suppose that a fetus is at a stage when it is considered permissible to be aborted. Suppose that the woman bearing the fetus decides, for some reason, that she would prefer that the child be born with no arms. To that end, she takes some kind of potion, and the child is later born with no arms. I think that most people would feel that the woman's action was wrong because it was wrong to deprive the child that was born of his or her arms and their use. But if that's true, why is it permissible to deprive the child that would have been born of his or her body and its use?

I'm not sure there's much of a puzzle here. If the woman takes the potion you describe, then at some future point there will be a child who has no arms, and that future child, one could easily argue, will then have a claim against its mother's earlier behavior. If the woman has an abortion, on the other hand, then at no future point will there be a child who has no body and, on that ground, has a complaint against its mother's earlier behavior. The point here is that the wrongness of the behavior, in the former case, can be traced to the fact that there will, at some point, be a person whose rights have been violated, even though that person was not a person at the time the rights were violated. There will be no such person in the latter case, unless of course you assume that the fetus in question is already, in the relevant sense, a person. But then that's an old argument.

Despite all the modern protestations of liberalism and political correctness, I have yet to meet a straight person who is fully comfortable with the idea of homosexuality. They claim to have no problem with the lifestyle, but inevitably succumb to negative gay stereotypes or latent discomfort (people are, I find, generally more accepting of me as a lesbian, but admit that they find the idea of gay men bizarre/wrong/funny etc). The increasing number of "out" gays seems only to have had an effect on the legal system, rather than people's general morality (and I do speak generally, from personal and first-hand experience alone). Why is it that the lessening gap between percentages of gay and straight people is not accompanied by similarly decreased prejudice? Imagine that the number of gay people outnumbered the straight population (unlikely, but I maintain that all humans are essentially bisexual) - would the minority straight population still see the gay population as "abnormal" due to the fact that they...

I'm not sure what the philosophical question is here. I suppose it may be true that the questioner hasn't met "a straight person who is fully comfortable with the idea of homosexuality". I'm not really in a position to say. But maybe she should get out more. (Or visit my church.) Or maybe her standards are too high, and she is confusing an inability to see life as a gay man "from the inside" with "full comfort". I confess I'm not really in a position to imagine being gay. It's not something I've tried extremely hard to do, but, I don't know, it's not something I think I have much hope of doing either. Any more than I think I can really understand, from the inside, what it's like to be female, or a black American (let alone what it's like to be a bat). But I don't think that makes me uncomfortable with gay men. It's just that, on a certain level, I find it hard to relate to some of the gays and lesbians I know. There are aspects of their experience that are very far beyond me.

Suppose a woman decided, for whatever reason, to put a pregnancy 'on hold' indefinitely, even for the rest of her life, while the fetus was at a stage of development in which it is currently permissible to abort it. That is, the woman takes a potion and stays pregnant, but the fetus remains insider her and dependent on her, and it never develops any further than it already has. I think many people would find this morally problematic in ways in which they don't find abortion problematic. But where is the moral difference?

For what it's worth, I find it obscure why someone would wish to pursue this course of action, but I don't find it obviously to be morally objectionable in any way I don't find abortion morally objectionable. Suppose the woman instead removed the fetus without its being killed, and put it in some kind of suspended animation. Perhaps she thinks, "Well, maybe later I'll be ready for a child, and then I'll continue the pregnancy." It's not obvious why this would be any more objectionable than abortion, and I certainly don't see a difference between this case and the one in the question. Indeed, one might wonder whether, at certain very early stages of pregnancy, there is very much of a difference between this and what routinely happens in fertility labs.

Are we born with morality, a distinct human sense of right and wrong, or is our morality merely a product of our environment?

It's easy to be concerned that, whichever answer this question gets, that will somehow serve to undermine morality itself. If, on the one hand, our moral sense is one with which we're born, then it's, in effect, genetic, and our gut reaction to human suffering can be written off as a consequence of the evolutionary value of protecting the herd. But if, on the other hand, our moral sense is a product of our environment, then it looks wholly non-objective: Jones, who grew up in a wealthy New York family, might have a completely different moral sense than does Wang, who grew up in poverty in central China, and there's nothing to choose between them. It's just a matter of their different environments. What's really distressing, frankly, is that one actually hears this kind of concern expressed by the otherwise intelligent scientists---psychologists, mostly---who are working on this very question. But the danger isn't real. The sense that there is a danger here is due to a failure to distinguish our ...

How much of epistemology boils down to semantics? Sometimes it seems as though all we're really doing is trying to decide which situations warrant use of the word "know"; nothing actually changes in practice.

This is a deep and important question. But let me first correct an apparent misimpression: namely, that, if the central questions of epistemology are semantic questions, then they are unimportant or uninteresting. On the contrary, semantics---the study of meaning---is an important subject in its own right, and it is arguably of central importance in any broadly "conceptual" investigation. So, to the question. This is much disputed nowadays. There are some philosophers who think that many central epistemological questions are, fundamentally, questions about the meaning of the verb "to know". This group includes so-called contextualists, like Keith DeRose, but also philosophers like Jason Stanley and John Hawthorne, whose view is sometimes known as "situation-sensitive invariantism". On these views, our odd reactions to many of the puzzle cases are due to aspects of the way the verb "to know" behaves, or to certain not so obvious features of the concept of knowledge. Contextualists generally hold that...