Let's flip the question around a bit. Suppose I believe that people who hold certain particular religious views are likely to favor policies I don't like and oppose policies I like. That gives me a reason to worry that if I vote for a candidate of that religious persuasion, I'd be voting for someone who wouldn't share my views on things I care about politically. And surely that's an acceptable reason not to vote for someone. It seems pretty different from racism or homophobia. People who wouldn't vote for an atheist, I'd guess, typically believe that atheists differ with them on questions that they care about. They see a person's atheism as an indicator of how the person would vote if s/he were a legislator. That still doesn't seem like racism or homophobia. Except... Experience suggests that people who wouldn't vote for an atheist sometmes have at least this in common with racists and homophobes: they haven't actually subjected their beliefs to scrutiny. It's very common to find people who...

There's limited and local skepticism, based on serious reasons for doubt. That can be a very good thing. (One ought to be skeptical of what politicians or advertisers say, for example; we've got plenty of evidence that they're often less than reliable sources of information.) But then there's more global skepticism that calls into doubt in a wholesale way large swaths of what we normally believe -- typically not on the basis of specific reasons for doubt, but rather on the basis of top-down arguments. Many of us (not all) find the second sort of skepticism less than helpful intellectually. One reason: starting out with that sort of skepticism cuts of interesting lines of philoosphical inquiry before they get anywhere at all. Unless we set that sort of skepticism to one side, most philosophical projects don't even get off the ground. For example: if we start from the point of view of ethical skpeticism, then serious moral inquiry gets stopped before it even starts. There's another reason: at...

Offhand, it's not clear why we'd think there's a difference in status among these oppositions. Once we fix a point on a line as the "origin," it's still up to us which direction counts as ahead and behind. What's up where I am on earth is down from the point of view of folks across the center from me. And so on. Space is isotropic; any direction is as good as any other. (And just a side note: if we fix left and right, we haven't fixed up and down. Imagine holding your arms out and rotating 180 degrees around the axis they define. You'd flip up and down, and also ahead and behind.) Still, there are some interesting points in the neighborhood. In our space, there's such a thing as "handedness": you can't turn a left hand into a right hand by sending it along some path in space. Our space is "orientable." But some possible spaces are non-orientable as the surface of a Möbius strip demonstrates. Likewise, in our space, there's an absolute distinction between inside and out, but that's a fact about...

The best answer to your first question, I think, is that we do it that way we check scientific hypotheses in general: we make predictions, do experiments, etc. The details, of course, are best left to the physicists, but unless the worry is a skeptical question about scientific knowledge in general, we proceed in the usual ways that science proceeds: we look for experimental results that would be improbable if Newton were wrong, but probable if he were right. As for whether gravity exists, this question needs some clarifying, I think. Suppose we have good reason to think that bodies in the universe behave pretty much as Newton's laws say they should. On one way of looking at things, this is exactly what the existence of "gravity" amounts to: confirming Newton's laws (or some related set of laws) is what it means to confirm that gravity exists, because there's nothing more to gravity than nature acting in accord with certain laws. On another view, the existence of gravitation amounts to the...

Because it didn't evolve in any other species. That wasn't very helpful. More to the point, it may not even be true. For all we can say for sure, other hominid species (perhaps Neanderthal?) had language, but didn't survive. In any case, the question of just why a particular trait did or didn't show up more than once in evolutionary history may not have any clear or uniform answer. The philosophical issue here, I suppose, might be whether the fact (if it is one) that as useful a trait as language only appeared in one species makes some sort of difficulty for the theory of evolution. Someone might claim: if the evolutionary picture really is correct, we would expect to see many species with this trait. Being neither a biologist nor a philosopher of biology, I can't say for sure. But I'm strongly inclined to suspect that this just isn't a good reading of evolutionary theory. Given the complexity of language-capable brains, what might be surprising is that the ability appeared even once. But it...

My closet. More seriously, it isn't expanding into anything. The universe contains all of space-time. If it's expanding, this is a fact about the stuff that makes up the universe itself, and not about its relation to some other place/thing/void. So what does it mean to say that the universe is expanding? At least this: that distances between things (on average) are getting larger. One common analogy: think about the surface of a balloon that's being blown up. Imagine the ballon as covered with little dots. Then as the balloon expands, each dot will get further away from each other dot. The obvious objection is that the balloon is expanding into the space around it -- there's more than just the surface of the balloon. That's true. But that's why it's an analogy rather than a perfect fit. Although it puzzles the imagination, the math of space-time doesn't call for positing a container space for the expanding universe. The geometry is internal to the universe itself.

We need to keep two questions straight here: (i) why is it necessary that 2+2=4; (ii) why should we believe it's necessary that 2+2=4. The first question assumes that this is, in fact, a necessary truth, and asks what grounds the necessity. The second asks how we know. On the first: why is it necessary that 2+2=4? Part of the problem is to decide what would count as an answer. I'll leave it to wiser heads than mine to offer a thought. But I think your worry actually lies with (ii). Now of course, in some sense of "could," it could be that we're all utterly deluded, and in fact 2+2 isn't equal to 4 at all. All that this means is that I can't rule out beyond any possible doubt that we're utterly addled in ways we can't even imagine. But to quote my old colleague Dudley Shapere for the m ty- n th time, the possibility of a doubt isn't a reason for doubt. Translation: the mere fact that we can dimly imagine that we're utterly and totally confused about even the...

Perhaps it's not so much a principle as a widely agreed-upon norm for setting potential conflict aside. We could imagine a society where the rule that everyone internalized was quite different: the person on the bench should always give their seat up to the newcomer. That would be a perfectly acceptable arrangement, and so there's no deep principle here; either way of settling priority is fine. That said, someone who bogarts the bench for hours on end just because they got there first isn't playing nicely. They never got the point of their mother's admonition to let someone else have a turn.

But two qualifications to William's comments. First, not all arguments are susceptible to truth-table analysis. (For example: every horse is an animal. Therefore, every horse's head is an animal's head.) Second, there are plenty of good arguments (inductive arguments, for short) whose premises don't strictly imply their conclusions, but that make their conclusions probable given the premises. At least sometimes, informal fallacies aspire to inductive rather than deductive goodness, and so showing that the conclusion doesn't strictly follow from the premises is beside the point. Peter's point still applies however: we can show that such arguments are bad by showing that they have the same form as arguments that are patently bad. Here's a patently bad argument: most pets are mammals. Kiki is a mammal, and so (probably) Kiki is a pet. Any argument with this form is bad, even though the aim isn't to show that the conclusion strictly follow from the premises.

At least in the USA, political parties aren't monolithic. Though we're in a period where there may be more uniformity among Republicans (at least in Congress) than there has been historically, Republicans disagree among themselves, and any Democrat thinks ruefully from time to time of Will Rogers' famous quip that he didn' belong to an organized political party because he was a Democrat. People can follow their party or their church mindlessly, but that needn't happen. Many people belong to a political party because overall, the party fits their political values better than the alternatives, and because collective action is often more effective than hundreds of Lone Rangers acting on their own. But it's not unusual for members of Congress not to vote with their parties, and it's also not unusual for a registered Democrat or registered Republican to vote for a candiate of another party. So the comparison with the medieval Church seems a bit strained -- especially since the sorts of sanctions parties...