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There are certain kinds of moral belief that we view in a pluralistic manner, and others that we take to be absolute. For an example of the former, suppose that I'm a vegetarian who believes that eating meat is immoral. Most people would say that it's inappropriate for me to harangue meat eaters, since they are just as entitled to their beliefs about diet as I am to mine. By contrast, we don't reason this way about things like murder. I am not obligated to respect the beliefs of someone who thinks murder is permissible--on the contrary, I may be morally remiss if I don't try to stop or correct him. What explains the difference between these two kinds of moral belief?

It's an interesting question. Some thoughts.

Suppose Rufus believes that murder is morally acceptable. If I know of a murder he's trying to commit, then most of us agree that I'm not just allowed but even obliged to do various things to prevent it. (Telling the police would be the most obvious.) But if I have no reason to think that Rufus is planning to kill anyone, then while it's perfectly okay for me to try to argue him out of his view, most of us don't think it's okay to harass and harangue him about this admittedly despicable view. One reason for this is a matter of keeping civil peace; more on that below.

Of course, there may be gradations here. Suppose it's not just that Rufus thinks it's okay to commit murder; suppose he makes a career of trying to convince other people. We'd still think there are limits to how far we can go in protesting, objecting and so on, but the limits would be fewer than they'd be if he were just some random weirdo who wasn't likely to act on his views and also wasn't likely to persuade anyone else. I don't have a theory of what the boundaries would be, except to say that they'd depend on the details.

In any case, you're right that we make distinctions. If Rufus is about to go out and commit murder, it's more than okay for me to try to stop him. If he's preaching that murder is acceptable and I shout him down, I'm probably pardonable. If he's about to go out for a sirloin, then short of trying to talk him out of it, there's not much that it's okay for me to do. And if he's merely arguing that it's okay to eat meat, then conversation about it is pretty much the limit of what's appropriate. What are the differences?

One difference is specific to the example: many of the reasons for thinking it's wrong to kill animals for food have parallels when it comes to committing murder. But there are other reasons for not committing murder that don't have parallels when it comes to killing animals. The point is that it's hard to imagine a coherent view that forbids meat eating but permits murder. We might put it by saying it's clearer that murder is wrong than that eating meat is. We also might be willing to add that even if eating meat is wrong, it's arguably less wrong than murder. In any case, when one sort of judgment seems less clear than another, we're less inclined to impose our own conclusions in the former than the latter.

In other cases, it's not clear that one side has the intellectual upper hand. It's quite possible to hold a moral view and to recognize that someone can disagree without ceasing to be reasonable, let alone becoming a moral monster. In cases like this, a proper modesty about one's own wisdom calls for respecting the opposition. Going a step further, if you hold a moral view that's widely doubted, you may be in the right, and eventually it may even become clear to most people that you're in the right. But it's also possible that you're missing something that other people see and if there are reasonable people among your opponents, you've got a reason to take this possibility seriously. In cases like this, trying to persuade others is fine. Haranguing and harassing is not so fine and suggests that you may have a deficient sense of your own fallibility. And of course, imposing your view by force is out of bounds.

This is a sketch of a morally imperfect system, of course; it's sometimes gotten things badly wrong. But quite apart from having a sense of modesty about one's own wisdom, there's the question of what the world would be like if we didn't restrain ourselves in something like this way. There, we tend to suspect, lies chaos. And chaos doesn't seem like a likely route to moral improvement.

It is a common moral conviction that it is better to let many guilty people go free than to wrongly imprison a single innocent person. My understanding is that this principle underlies the presumption of innocence in criminal trials. I can see that this strikes us as profoundly right, but I'm not sure why. I mean, off the top of my head it seems fairly easy to refute it along a crudely utilitarian line: all we need is to suppose that the guilty parties are liable to do harm enough to outweigh the suffering of the wrongly imprisoned innocent party.

Setting aside the question of whether the principle 'better to let many guilty go free than to wrongly imprison a single innocent person' is the rationale for the presumption of innocence, that utilitarians would reject the principle is not as clearcut as you appear to assume. We seem to be considering two possibilities:

(a) letting some number of guilty persons (you say 'many') go free but thereby ensuring that an innocent person is not punished
(b) punishing an innocent person but ensuring that 'many' guilty persons are also punished

For utilitarians, the question of whether (a) or (b) is morally preferable will turn on empirical facts or tendencies. You suggest that utilitarians will opt for punishing the guilty even at the cost of punishing the innocent "if the guilty parties are liable to do harm enough to outweigh the suffering of the wrongly imprisoned innocent party." I suspect this move overlooks two factors that might tilt the balance of costs and benefits (happiness and unhappiness) in favor of (a):

First, punishing people has costs. Suppose that "many" here is 10 guilty persons and that punishment we're considering is incarceration. Incarcerating a person in the United States costs $14,000-60,000 per year ( So if we follow (a), no one is punished, so the cost of incarceration (in this example) is zero. But if we follow (b), then 10 guilty persons and one innocent person is punished. That comes out to $154,000-660,000 per year. That's a lot of money in its own right, with significant opportunity cost. (How many teachers could we pay, how many roads could we repair, how many essential surgeries could we provide, etc., for that amount of money?)

Second, (b) has the difficulty that it's likely to undermine the deterrent function of punishment, which is a crucially important consideration for utilitarians when it comes to morally justifying punishment. The reason for this is that individuals will presumably come to understand that they can become liable to be punished even if they make every conscientious effort to be innocent, that is, not to commit crimes. A likely effect of (b) will be that many will commit crimes figuring that there's no particular benefit in not committing crimes, given that (under scenario (b)) there's a significant chance of being punished anyway. Put differently: If there's a decent chance of being punished regardless of whether you engage in crime or not, what reason of self-interest do you have to refrain from crime if the crime benefits you?

Again, I'm not suggesting that (a) is obviously morally preferable to (b) from a utilitarian perspective. But once we take all the likely costs and effects into account, the case for (a) being preferable to (b) looks stronger than you appear to assume.

I would really like to know what logic is. The Stanford Encyclopedia of Philosophy has TOO MANY articles on logic for someone like me. Let me list most of them: action logic, algebraic propositional logic, classical logic, combinatory logic, combining logic, connexive logic, deontic logic, dependence logic, dialogical logic, dynamic epistemic logic, epistemic logic, free logic, fuzzy logic, hybrid logic, independence friendly logic, inductive logic, infinitary logic, informal logic, intensional logic, intuitionistic logic, justification logic, linear logic, logic of belief revision, logic of conditionals, logical consequence, logical pluralism, logical truth., many-valued logic, modal logic, non-monotonic logic, normative status of logic, paraconsistent logic, propositional dynamic logic, provability logic, relevance logic, second-order and higher-order logic, substructural logic, temporal logic. I have started reading some of these articles, but I still didn't find an answer for my basic question. In some of these articles, a logic (<i>a</i> logic!) seems to be just a bunch of symbols intended to represent reasoning. But some other times I get the idea that logic intends to discover what is good reasoning. In any case, why are there so many different logics? Are they all necessary or useful? Don't computers use just one kind of logic? Truth is that if my children (6 and 8 y.o.) ask me what is logic, I don't know what to tell them....

At the risk of a bit of self-promotion, readers might find my introductory article on logic for the Encyclopedia of Artificial Intelligence to be helpful. You can read it online at

Could there be colours we haven't yet seen?

A lot depends on who "we" are. Suppose we are complete achromats, so that we only see "achromatic colours", greys, blacks and whites. Now it is clear enough that there is a colour "we" haven't seen. Red is an example, and so are all the other chromatic colours. Now what if "we" is the whole human race at all times. We can imagine that we take the set of all the colours that anyone has ever seen. Question: are there more? Wittgenstein is someone who takes a negative line on this. Are they colours that others might see which we do not? '. . . [W]e would still not be forced to recognize that they see colours that we do not see. There is, after all, no commonly accepted criterion for what is a colour, unless it is one of our colours' (Wittgenstein, Remarks on Colour I, 14). We do not use colour language just by pointing to colour samples and naming them. It takes more to be talking about colours than that (III, 58). The idea of little coloured patches of colour is not a "more fundamental" idea of colour than our actual idea. We have to ask questions such as 'How do we compare colours?' to be sure we do have the concept of colour at all. When we say bees see in the ultraviolet, which they do, are we forced to say that what they are seeing there is colours? How would we compare the colour violet with what the bees "see" - if seeing is what it is?

so What is more real? The number two or my two feet?

Why must either be "more real" than the other? I can't make sense of "more real," anyway, as a comparison. Are shadows less real than the 3D objects that cast them? Shadows are dependent in a way in which 3D objects are not, but I don't see how that makes shadows any less real when they exist.

Some philosophers say that the number 2, being an abstract object, exists necessarily (i.e., in all possible circumstances), whereas your two feet exist only contingently (i.e., in some but not all possible circumstances). But that view does not imply that the number 2 is any more real than your two feet.

Other philosophers say that the number 2 exists but not your two feet, because they say that "anatomical foot," being a linguistically vague term, fails to denote anything in the world. (I think they're mistaken.) Still other philosophers would say that neither the number 2 nor your two feet exist. But none of that, I think, implies that one is more real than the other. Is Donald Trump more real than the Tooth Fairy? There is such a thing as Donald Trump but no such thing as the Tooth Fairy, yet I don't think that makes the former more real than the latter: "more real" isn't a comparison like "more controversial."

Here is a question. Say I want to live forever and constantly move my brain from one body to another, so I never age. I also replace non functioning parts of my brain with new ones made with stem cells. Eventually after living for a long enough time my brain is no longer anything like the original except for its collective memories. Would that thing still be me? To take it a step further I create clones of myself and each of them has a small part of my originals brain. Would I still exist? Or I created a collective consciousness in which I am able to communicate to each of my clones and we are able to share our experiences in one big cloud. What does that even mean for me? Am I even the same person or something completely different? These problems have been really bugging me and I am just trying to see if anyone has any answer.

Often with questions that are composed of multiple further questions ("Here is a question", you write . . . - it's not - I count four question marks!) it helps to take just one, and deal with it carefully, before moving on to the next. Of course some of the sub-questions will generate further questions, but that simply means that some patience is required. For example, 'I move my brain from one body to another, so I never age.' Why does it follow that you never age? If you retain your memories (line 3) and add to them, then you are changing and aging, psychologically. So you must mean that you don't physically age. But the brain does age. And why is it that 'I never age' follows from 'I move my brain from one body to another'? That seems to assume that who you are is a matter of having the same brain. Is that right? And if it is, then if as you say 'after living for a long time my brain is no longer anything like the original' then you are not after all the same person, so the question goes away. A quick thought to end, and to encourage you to continue with the problems you raise on your own, till they stop bugging you. If I sneeze, it is not the case that my brain sneezes. So I am not my brain. Questions like yours are common in the philosophy of mind, and there are lots of things to read and think about. The right place for you to start might be with fission ideas in the work of Derek Parfit. For him if I fission, the answer to the question whether I survive is indeterminate. You might also look at the entry "Personal Identity" (the section on fission) in the online Stanford Encyclopedia of Philosophy. Good luck to you, and to your brain, whichever gets there first.

Milo Yiannopoulos recently resigned from Breitbart amid controversial comments about that a relationship between an adult male and a teenager could be beneficial. Without wishing to imply a defence of his claims, what I wanted to ask is -- didn't Socrates make essentially the same claim 2500 years ago in the Symposium, and what has changed between now and then to make the idea less intellectually respectable?

A lot that Milo Yiannopoulos said about sex calls the Symposium to mind, and for all I know was intended to. He distinguished between relations involving pre-pubescent children and those involving teenagers past the age of puberty, and the latter type certainly existed in Plato’s time. Moreover the relationships discussed in the Symposium take place, with very few exceptions, between males.

But let’s subdivide your two questions into three. 1) Did Socrates claim that adult/teenager relationships could be beneficial? (You don’t specify to whom they would be beneficial, but I assume you mean “to the teenager.”) 2) Were relationships of this kind considered normal in Socrates’ time? 3) What has changed since then?

It’s worth adding question (2) because Plato presents Socrates attempting to give a philosophical interpretation and clarification of existing practices. What he says makes fuller sense if we recognize what was being done in that time and place. Thus it’s not that Socrates saw people around him engaging in relationships exclusively among adults and proposed that they seek teenage partners.

What was actually done in antiquity is notoriously difficult to determine. The written evidence comes for the most part from elite authors; visual evidence is available on vases, for example, but it stands in need of interpretation. Beginning with Kenneth Dover’s Greek Homosexuality in 1978, modern authors have tried to refine our conception of what was done in antiquity and how it was perceived. Some of Dover’s claims have been challenged or superseded: David Halperin, Martha Nussbaum, and James Davidson are three authors worth consulting for informed and thoughtful explorations of the issues at stake. On broader questions about ancient conceptions of sex, the anthology Before Sexuality (edited by Halperin, John Winkler, and Froma Zeitlin) is excellent.

One great difference between the time of Socrates and Plato and our own time is the change in attitudes toward male same-sex love and desire. An erotic relationship between two men has carried enough of a stigma in most of the modern world that making one of the two a teenager only intensified the social disapproval already attached to homosexuality. In ancient Greece, by contrast, and even when there were prohibitions in place about sexual practices, the desire for someone of the same sex does not seem to have been treated as problematic or strange.

But given that different social backdrop, what Socrates says in Plato’s dialogues still stands at some distance from what Yiannopoulos says. In the Symposium he reports a theory of love that he attributes to a woman named Diotima (and I’ll treat this as what Socrates is saying for our purposes). It clearly indicates that love, or eros, can begin as attraction between men. But Socrates does not talk about older and younger, as other participants in the Symposium’s conversation to (especially the characters Phaedrus and Pausanias). In fact he does not say much about the object of love at all; he’s interested in the one who feels desire and what that desire is like. One makes progress in erotic attraction by going from a single beautiful body to appreciating the beauty in all bodies, and from there to appreciating the beauty in all souls. And even that is not the end of the story, for the lover who pursues beauty then advances to loving the beauty in customs, then the beauty in every kind of knowledge, and finally beauty itself.

Is this beneficial? Without question. It’s the benefit of becoming philosophical. But the benefit goes to the one who feels the eros, while human objects of love quickly disappear from view altogether. Again: Socrates is speaking to people who assume that romantic, sexual relations are going to be paradigmatically those between older and younger male partners, but he does not talk about human relationships.

What Socrates says in another dialogue, the Phaedrus, is closer to what your question asks about. In the Phaedrus Socrates describes erotic pursuit in which one partner is an older man, the one who feels eros or desire, and the other is a younger man who feels something referred to as “counter-love,” a returning desire that is not quite as strong as the older partner’s emotion. (David Halperin’s article on anteros is particularly valuable.) The relationship between the two of them is much more clearly a love-relationship than anything Socrates advocates in the Symposium is, and the benefit goes to both. They both can become more philosophical under the influence of the love between them than either one would have become alone. And the younger partner learns how to be more like the kind of god whom his soul resembles; so there’s a particular pedagogy at work in the relationship.

But the very word “relationship” leads us to an important difference from Yiannopoulos’s claims that needs to be spelled out. In the Phaedrus the love Socrates describes has to be non-sexual. Those who give in to sexual desire quickly lose the benefits that love has to confer on human beings. Their relationships are bound to be erotic, and what we would call romantic, but Socrates does not allow them to turn into sexual relationships.

So what has changed from Socrates to our time? First of all there is Socrates’ faith that erotic attraction can work productively with philosophical enlightenment. People would be less likely to believe that any more.

Second is the change I already noted between a society that did not perceive homosexuality as peculiar and one that does.

Third, attitudes toward inequality in such relations have changed since antiquity. It was important to men in classical Greece to be the active partners in sexual relations. I have been discussing male-male relations, but when you look at male-female relationships, as between husbands and wives, they aren’t the breath of fresh air that Yiannopoulos might present his views as being. A man of thirty might take a bride of fifteen and immediately start trying to produce offspring. Whatever the reason is behind our cultural transformation to prohibiting this kind of marriage, the reason should be applauded. In many respects we value equality in love relations to the same degree that the ancient Greeks presumed and valued inequality. And if you value equality, your first reply to Socrates might be: How can we learn from erotic attachments and become more philosophical through those attachments when the partners in them have an equal role? Why does learning have to mean learning from a superior?

The Constitution may prohibit discrimination on the basis of religion, but should common sense? After all, to give extreme examples, religions have advocated such things as cannibalism and human sacrifice. What stops people concealing any sort of immorality or false beliefs under the label of religion?

First a point about "discrimination." The Constitution prohibits government discrimination against religion, but it doesn't, for example, prohibit me from refusing to associate with known worshipers of the Great Spaghetti Monster. So we'll take it as read that government discrimination is what's at issue. With that in mind...

Cannibalism is illegal whether or not it's done under the banner of religion. So is human sacrifice. More generally: various kinds of conduct are either illegal or could be made illegal if that seemed to be the right thing to do. That means it's not clear what's gained by outlawing religions that supposedly advocate such things.

Maybe someone could say that advocating bad things should also be illegal, whether done in the name of religion or not. And depending on what we mean by "advocate," that's already true in some extreme cases. Conspiring to commit a crime is illegal. Inciting a riot is illegal. But the Constitution and American political mores give people very wide latitude in what they can advocate for --- even if it's something most of us find abhorrent. We make a sharp distinction between speech and conduct. Among the motivations for this is a healthy suspicion about government. Governments that get into the censorship business don't have a good track record of doing it wisely.

That's related to another point. "Facts" about what religions do or don't advocate are anything but simple. For example: in the Hebrew Bible (or, as Christians refer to it, the Old Testament) there are dicta that call for putting adulterers to death. (See Leviticus 20:10). To conclude from this that Judaism or Christianity advocates the death penalty for adultery would be just plain wrong. And to argue that these religions really do advocate such a thing because their scripture demands it would be a shockingly simple-minded way to think about the relationship between a religious traditions and its texts. Having the government decide what some religious tradition "really" advocates assumes (among many other things) that legislators or civil servants have some special insight into such things when in fact there's not the slightest reason to think they do. But even if some religious tradition unequivocally held that we should execute adulterers, we're back to the earlier point: our legal tradition (wisely, I'd say) maintains a pretty sharp distinction between what people say and what they do.

There's a further problem. Christianity, for example, is no one thing. Nor is Judaism nor Islam nor Buddhism nor... Within a religion tradition we often find sharp disagreements about what's acceptable and what's not. Does "Christianity" forbid same-sex marriage? It's a confused question. Within Christianity there are people who argue on both sides. Each side may think the other is confused about what authentic Christianity requires, but in any case, getting the government in the mix doesn't sound to me like a recipe for making things better.

Summing up, it's hard to see what good could come from having governments sort out which religions are acceptable. However, it's all too easy to see the sorts of things that could go wrong.

Do people have the right to rebel in a democracy? Is it just?

What makes this issue tricky is that the question seems to equivocate on the notions of "right" and "just."

Suppose (as seems likely) that rebelling against a democratic government involves conduct that the government in question has declared illegal. It seems clear that such rebellious conduct can't be "right" or "just" in the sense of of being legally permissible. It would, after all, threaten incoherence if a code of law has an 'out clause' permitting rebellion, akin to "here are the laws, but you can rebel against them without penalty." That would render that system of law toothless with respect to its authority.

So if there is right to rebel, the right can't be a legal or political one. It would have to be a moral or "natural" right. Indeed, this seems to be what political theorists such as Locke (and the framers of the U.S. Constitution he inspired) had in mind when they referenced a right to rebel against unjust governments. I won't take on the big project of defending the existence of such a right. But I hope you can see that your question has a complex answer: in a political or legal sense, no; in a moral sense, perhaps.