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Hi, I'm a biology student who often uses biology as a framework for understanding thought. I've come to a really tough crossroads of thought. What differentiates cognitive biases from logical fallacies?

The difference between the cognitive biases and the logical fallacies is that the biases can be taken to be common built-in tendencies to error of individual judgements, whereas the fallacies, both formal and non-formal (so-called "informal", badly named because "informal" actually means "casual" or "unofficial" or "relaxed") are types of argument. The point is that the biases can be said to have causes, and are hence of psychological but not logical interest, whereas the fallacies do not have causes (though the making of a fallacy on a particular occasion may have) and the reverse is true. There is more to be said, of course, because a psychologist might take an interest in the fallacies.

Is it easier to love or be loved? I have tried to be loved by people, but I usually get pushed away. I guess I'll never be loved. All I can do is love and take care of other people.

When you write "I guess I'll never be loved," I think you might be able to change that right now. You can love yourself. You may already have proper self-love, but if not, self-love and acceptance can be an important means to finding love with others. I am pretty sure that if I lack self-love and instead hate myself, I am probably not in a good position of being in a loving relationship with another person: I might be baffled with thoughts like "why does she love me when I know that I am not worthy of attention, let alone love?"

Philosophers have come up with various philosophies of love and this site would not be big enough to fill all these positions out. But I can record an answer to your first question by a famous philosopher, Kierkegaard. He thought it was easier to love than to be loved. To love, you do not have to depend on how your beloved responds. You can love him or her without requiring or expecting love in return. Of course that can also be a hard, non-compensatory love. It is, though, in the mind of Kierkegaard and some others, something that can be beautiful.

What do we mean by the assurance, "It's not personal"? Why is that supposed to mollify us?

Great question! It might mean different things in different contexts! When a firefighter tells you this after rescuing you, she is probably trying to prevent you from thinking she is the new love in your life. "It's all part of the job" sort of thing. In the context of philosophy, the expression probably comes up when one philosopher is criticizing another. Aristotle says something like he has loyalty to Plato (his teacher for 20 years) but he loves truth more. He might have said: "Plato. My not accepting your theory of ideas and the soul is not personal." I suppose the expression conveys (on occasion) that mutual affection, even close friendship, is not a guarantee of agreement or loyalty to the views and arguments at issue. In that sense, while the expression may not "mollify" it might be intended to convey the message that disagreement does not mean personal disrespect or (even) lack of love for the persons involved.

Still, I am drawn to the (at least general) idea that philosophers should take their responsibilities personally. If I am a failure in class or seminar room and I realize I did not respect members of the class, I think I should take that personally insofar as it is a failure of myself as a person and in the practice I have devoted my life to. Perhaps one should "not be personal" in the sense that one should be "objective," but insofar as "being personal" means taking matters seriously as a person with commitments and practices, then I think it might be good if, in the course of a dialogue, someone said "it's personal" if they mean that they --as persons-- are invested in the dialogue. They are all in.

Not intending to mollify, but trying instead to stimulate further reflection.

Assuming that trees are not conscious, is there anything morally wrong with cutting down a tree that has survived for a thousand years?

It is most certainly not true that non-conscious things can be destroyed without reason, or just for the reason that they are not conscious. What is wrong with slashing or burning a Rembrandt painting? The answer is not that there is nothing wrong, because the painting is not conscious, but that there are many things wrong, including aesthetic ones, and historical ones, and the fact that the painting does not belong to to the slasher. Of course it would be even worse if the painting were conscious. And even if it belongs to the one who destroys it, it is unclear that he has the right to destroy it. A question might still arise. Is the painting part of the national heritage? This sort of consideration is relevant with Grade I, II* and II listed buildings in the U.K. Or what would be wrong with burning the only Penny Black remaining in the world just for kicks? About the 1000 year-old tree, now. The mere fact that it has survived for that long, for nearly 1000 years since the Norman Conquest, to put it in perspective, should give one pause. Then there is the fact that the tree may be a thing of majesty and beauty. There is also its place in the ecosystem. Is it a vanishing species? Or perhaps it is a home for many other species, and not just squirrels, which can be a pest, but birds, for example. What happens to such dependent species? There is also the general question of deforestation to consider. So the reasons for which it might be morally wrong to destroy it are virtually endless.

Dear Madam or Sir, this is not a question but a request: Is there an introduction into philosophy that you would recommend? Hoping to get an answer I remain sincerely yours Matthias

There are basically two kinds of intro philosophy texts: General intros and anthologies of "classic" papers. As Andrew mentioned in his reply to your question, a search on will turn up many good anthologies. But the two general intros that I heartily recommend are:

Nagel, Thomas (1987), What Does It All Mean? A Very Short Introduction to Philosophy (Oxford: Oxford University Press)

and an "oldie but goodie":

Russell, Bertrand (1912), The Problems of Philosophy, various editions and publishers

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."