Let's say there is some crime committed and that only 5% of similar crimes are committed by someone like Person A (based on demographics, personality type, previous criminal record, etc.). If the police later find evidence suggesting that Person A is the perpetrator of a crime and that there is only a 10% chance that the evidence could exist if Person A is innocent, then does that mean there is a 90% chance that Person A is guilty? Or do we have to factor in the fact that there was only a 5% probability that A was guilty before the evidence was found? Thanks!

What we're trying to get to is the probability, given all the evidence, that A is guilty. Let H be the hypothesis that A is guilty. You're supposing that our initial probability for H is 5%, i.e., .p(H) = .05. Then we get a piece of evidence – call it E – and the probability of E assuming that H is false is 10%, i.e., p(E/not-H) = .1. Your question: in light of E, how likely is H? What's p(H/E)? We can't tell. We need another number: p(E/H). We need to know how likely the evidence is if A is guilty. And we can't infer that from p(E/not-H). Why not? Well, suppose the evidence is that the Oracle picked A's name out of a hat with 10 names, only one of which was A's. The chance of that if A is not guilty is 10%, but so is the chance if A is guilty (assuming Oracles don't really have special powers.) iI this case, the "evidence" is actually irrelevant. The crucial question is this: what's the ratio of p(E/H) to p(E/not-H)? Intuitively, does H do a good job of explaining E? And knowing only one...

Many of those who favor online piracy (or who oppose restrictive laws meant to combat piracy, at least), argue that piracy does not actually hurt movie and music producers. They claim that most pirates would be unlikely to buy the products in question even if they were unable to download them for free. In restricting piracy, we aren't actually restoring revenue to the producers or anything of the sort. Those producers would be just as successful or unsuccessful whether piracy were allowed or not. Is this sensible? Let's say that I download a movie. If it is really true that I would not buy the movie in any case, does that make downloading it okay?

One thing is clear: if everyone downloaded for free, content producers wouldnt be able to profit from their labor. One reason why I don't downloaded pirated music, movies, etc. is that I think filmakers, musicians, etc. should be able to make money by doing what they do, and I can't see what's so special about me that I should be entitled to benefit for free from what they do. That's a long-winded way of saying I think it would be wrong for me to download pirated copies. Even though the filmaker would never get Freddy Freeloader's money, if. All did as Freddy does, the filmaker would suffer and in the long run, so would we all. Having said this, I think there's an awful lot wrong with contemporary copyright and intellectual property law. It could even be (though I'm not in a position to say so) that copyright law as it stands does as much harm as good. It could even be (though I doubt it) that we'd be better off if there were no intellectual property laws and we just depended on people's sense...

Suppose that you had two bags each with an infinite number of blue marbles. Suppose you also had another bag of infinity red marbles. If you mixed those three bags what are your odds of getting a red marble? Obviously this isn't a realistic experiment but is it 1 in 3 or 50%?

I'd suggest that there needn't be a determinate answer without adding more detail. In particular, the notion of "mixing" the three collections would need to be spelled out. Suppose the "mixing" works this way: take 10 marbles from the red bag and one from each of the blue bags. Put in an infinite vat and stir. Repeat ad infinitum. (We could imagine the first operation is performed in 1 minute, the second in half a minute, the third in a 1/4 minute…) The intuitive thought is that a "random" draw is most likely to give you a red marble. (10 chances out of 12). This may seem contrived, but only because we have some other loose, unspecified idea of mixing that we're comparing it to. The point is simply that the problem, as stated, doesn't determine the answer.

I am wondering how philosophers try to resolve ethical dilemmas in which both sides have reasonable claims to be "right." In particular, I'm wondering about the conflict recently in the news between a woman's right to contraception and an employer's right to refuse to do something considered sinful by his religion. As a more specific example, consider a woman's right to obtain a medicine such as Plan B in a timely manner (say, a woman in an isolated town with only one pharmacy, to whom a pregnancy is likely to prove fatal, and who was raped by her brother) and a pharmacist's right to refuse to dispense such a medicine because he considers doing so the equivalent of committing homicide. Is there any method of resolving such a dilemma in a way that recognizes the ethical arguments of both sides?

An interesting question. Without trying to settle the issues you use to raise your question, I'd suggest that there's no sure-fire method to be had here, and that while philosophers have things to contribute, they don't have any sort of magic wand. Ethical conundrums come up when different ways of looking at an ethical question suggest different and incompatible answers, and when the different approaches have some serious plausibility. Many people will agree: there's something to the idea that a woman who wants the Plan B medication ought, other things being equal, to be able to get it. But many of those same people will agree that in general, people shouldn't need to violate their consciences to practice otherwise respectable professions. Put briefly, both sides have plausible starting points. This is true of a good many serious disagreements, ethical or otherwise: the right answer isn't obvious, and different answers are prima facie plausible enough to be taken seriously. So what do...

what is the fundamental difference between science and non-science? aware of popper's theory of falsification, i still am unsure of how a theory can only be scientific if it can be proven false? this seems rather contradictory; what about if a scientific theory had been rigourously tested so much that it is in fact true, and cannot be proven false? thanks in advance :)

I'm not sure there's a fundamental difference between science and non-science. But the point about falsifiability isn't that a true theory can be proven false. It's that scientific theories can be tested, and we know what sorts of results would count against the theory in principle Keep in mind that even a theory that's survived a long string of rigorous tests might still be overthrown. The point of the falsifiability requirement is that we know what sorts of results would count against the theory - whether or not they ever turn up. One more point, though. It's one thing to say we know what would count against a theory. It's another to say that some particular bit of evidence would refute a theory conclusively. Things are seldom if ever that simple.

Is there any moral justification for income taxes? If a person receives an income through the exchange of his services to an employer, who then grants that person a wage, how can it be justified to force the person to relinquish some of his earnings or else face violent coercion? I understand that from a utilitarian standpoint, taxes are justified if the services they provide increase overall happiness, but hasn't this understanding of utilitarianism been largely forsaken because of it's inability to adequately deal with individual rights?

Others can no doubt give more nuanced answers, but most people (I'd be wiling to say virtually all) who earn a living depend either directly or indirectly on government-supported institutions and government-provided infrastructure for the possibility of their livelihood. This includes but is not limited to - military defense against external aggression, a police force, a court system to enforce legal rights, a public education, system, highways... A setting in which a worker can avail him/herself of none of those things is a setting in which very few indeed would prefer to work.

Hello Philosophers! Can anyone defend the Ontological Argument against Kant's criticism that existence is not a predicate?

Sure. Even if existence is not a predicate, it's at least arguable that necessary existence is. (As Norman Malcolm pointed out years ago, there really are two versions of the argument, and the second one deals with necessary existence.) We doubt that existence is a predicate because, roughly, saying that something exists tells us nothing about what it's like. Not so for necessary existence. Not just anything could exist necessarily. The computer I'm typing on is the wrong sort of thing to be a candidate for necessarily existing thing. Assuming that some things are of the right sort to exist necessarily, necessary existence would be a predicate. Whether this is a defense of the argument all things considered is another matter. But I think the point made here is fair as far as it goes. A being that merely happened to exist wouldn't be a being than which none greater can be conceived.

What is the difference between a "fallacy" and a "cognitive bias"?

How about this? A fallacy is an actual mistake in reasoning. A cognitive bias is a tendency to commit certain sorts of mistakes. Not all fallacies are the result of cognitive biases, and having a cognitive bias doesn't guarantee that you'll commit the corresponding error.

Is there any coherent non-religious argument that shows that the appearance of life on the universe is a "good" or "valuable" thing? It seems to me that something is valuable iff there's somebody who values it. So life would not be valuable when it does not exist, but it would become valuable when it does exist? Would it value itself? I'm not sure if this circular reasoning, or there's some solid ground. What would be some standard literature on this kind of issues?

An interesting question. I'd start by suggesting that your "if and only if" is open to challenge. First the less important part for our purposes: the fact that somebody values something doesn't obviously mean it's actually valuable. Some people value terrible thing, after all. There's a chilling scene in James Clavell's novel Shogun in which a samurai takes deep, deliberate and despicable pleasure in the screams of a man being tortured to death by a torturer who specializes in optimal cruelty. The samurai clearly values the experience, but I'm not willing to say that it's therefore valuable . Still, it seems right that value has a deep connection with experiences and the beings who have them. That may seem to be all that your worry needs. In other words it might seem that something is valuable only if someone values it or, more broadly, only if it evokes the right sort of reaction in some sentient being. But this is too strong. Consider: something could be exquisitely beautiful (to take...

This question is vague. Possibly too vague. You decide. Interpret the question as you will, I have not narrowly defined each word. I recently decided to live the ethical life. I want to hold myself up to the standard of doing the best I can. My automatic interpretation of this is utilitarianism. In fact, this seems like the obvious answer to me. But as I can see, no one ethical system is completely accepted, not utilitarianism either. As someone who knows more than I do, do you think the first step to the ethical life for me is to study ethics, or to follow my gut instinct and use my basic understanding of utilitarianism or "as much happiness generated as possible" to guide me?

Good for you for taking what's right so seriously! As for general advice, a few quick thoughts. First, though utilitarianism undoubtedly provides useful insights, it's not really clear that utilitarianism always gives the best answers. A quick example: the fact that a mafia leg breaker gets satisfaction and enjoyment from his work arguably carries no weight at all in deciding what's morally best. Perhaps the utilitarian can explain this, but only perhaps. And that leads to the second point. It may be that the study of ethics tends to lead people to better moral decisions, but that's very doubtful. (Don't be so sure that the people on this panel know more than you do.) In any case, it's hard to believe studying ethics necessary for being good. Whether I'd turn to someone for moral advice and whether they've studied ethics don't have much to do with one another. But simply trusting one's gut isn't always best either; gut feelings are often wrong. So what's the positive advice? A good deal of...

Pages