No. Alice may think that Jones is a genius; Bob may think he's a fool. He might be neither.

At least part of the answer to your question is hidden in the way you phrased it. Suppose that I'm wired so that there's really nothing I can do about the fact that I think inductively. As soon as I put my copy of Hume down, I revert straightaway and irresistibly to making inductive inferences. We usually 't think it doesn't make sense to criticize people for things they have no control over. If we can't help making inductions, then criticism is pointless. But we don't think that all non-rational beliefs are like this. On at least some matters, we're capable of slowly, gradually changing the way we think until the grip of the irrational belief weakens to the point where we can resist it. For example: someone might realize that they're prejudiced against some group. They might come to see that this prejudice is simply irrational. That might lead them to think they should try to change the way they think and react, and they might well succeed . Or to take a different example, when cognitive...

I hope that some of my co-panelists who think more about decision theory will chime in, but here are a few thoughts. Cheap first try: it seems plausible that even if every additional dollar brings some marginal utility, by the time we reach, say, a trillion trillion dollars (a septillion dollars) the utility provided by the septiliion+1th dollar is so tiny that the utility cost of worrying about it exceeds the utility it could provide. Of course, that's not really an answer to your question. What you have in mind is a scenario on which it's not just that each additional dollar adds utility, but on which the total area under the utility curve goes to infinity. But it's worth noticing that these are separate ideas. Even if each additional dollar adds value, the infinite sum might still converge to a finite number. So we can restate the problem this way: there's an infinite well of utility available, and you can choose to have any finite amount of it, but you have to specify the quantity...

It might help to start with some definitions. As philosophers and logicians use the term "valid," a piece of reasoning is valid, roughly, if it's impossible for the premises to be true unless the conclusion is also true. That means that any argument with true premises and a false conclusion is automatically invalid. And as philosophers and logicians use the word "sound," a sound piece of reasoning is valid and has true premises. That means that any sound argument automatically has a true conclusion. Of course, valid arguments can lead us to bad conclusions. That happens when they start with false premises. The following argument is valid, but the conclusion is false: Some whales are fish. All fish have gills. Therefore, some whales have gills. The problem, of course, is the first premise. But the reasoning isn't at fault. So far, we've talked about deductive reasoning, and we can say that there are principles of deductive reasoning that are reliable in this sense: when applied to true...

It sounds as though you're giving a version of Pascal's Wager . One version of that argument runs along the following lines (whether or not this is exactly what Pascal had in mind): If God exist and I believe, I'll get infinite bliss. If he exists and I don't believe, I'm damned. But if God doesn't exist and I believe, I lose little, if anything and if he doesn't exist and I don't believe, I don't gain that much. Since belief potentially gains me much and loses me little, but since disbelief potentially gains me little and loses me much, I should believe. One problem, of course, is whether skeptical people can actually get themselves to believe. Pascal thought they could by going to mass, taking holy water and the like. Let's suppose he's right. What's the downside? One famous difficulty is the "many gods" objection. Which version of God do we believe in? What sorts of actions should we perform? Should we be Christians? What if there's a God who sees that as an unacceptable form of thinly...

Only if you define "rationality" in a way that makes it opposed to emotion. But for a lot of reasons, that would be a dubious definition. For one thing, we have reason to believe that intelligent decision-making isn't disconnected from emotions. There's been a good deal of work on this topic by philosophers and scientists, but one well-know place to start is with Antonio Damasio's book Descartes' Error . It turns out that the emotional centers in the brain have an important role to play in helping keep us on the rails. We can add: other things being equal, it doesn't sound rational to choose a life that makes it less likely that we'll be happy and fulfilled. But for most of us, a good deal of what makes life meaningful is bound up with our emotions. In a perfectly obvious sense of "rational," it's rational to seek love, let ourselves cry in the face of tragedy and open ourselves to joy. A concept of "rationality" that ruled all this out would be poor and perverse.

I don't believe in them myself, though I'd be quite willing to be convinved that some of them are true. However, the story you tell illustrates a typical difficulty of these accounts: we might grant that your in-laws saw something , but what was it? The acronym "UFO," of course, stands for " Unidentified Flying Object." And that's what we have if we take your in-laws' story at face value. We certainly don't know that whatever it was came from outer space, as they used to say. Of course, some stories say more. As you point out, we get tales of abduction, strange beings and the like. Apparently many of the people who make these reports seem otherwise sane and normal. Do we know that what these people say isn't so? I wouldn't say that we do. After all, it's surely possible that there is intelligent life elsewhere in the universe, and that some of it has made it to where we are. But many of the cautions that the 18th-century philosopher David Hume applied to miracle stories seem to apply...