In Aristotle's syllogistic logic (including in his square of opposition), "All men are mortal" implies "Some men are mortal." But in the standard logic of the past 100 or so years, that implication doesn't hold. This failure of implication arises because modern standard logic construes "All men are mortal" as a universal quantification over a conditional statement: "For anything at all, if it's a man then it's mortal." Intuitively, I think we can see why the universally quantified statement can be true even if no men exist. Compare "For anything at all, if it's a unicorn then it's a unicorn," which seems clearly true despite the fact that (let's assume) no unicorns exist. In modern standard logic, then, "All men are mortal," "No men are mortal, " and "All men are immortal" come out true if in fact no men exist. Importantly, "Some men are immortal" does not come out true in those circumstances. A similar lesson applies in set theory, in which "All of the members of the empty set are even" and...

My perspective: Even if matter hasn't always existed, something or other has always existed (which is compatible with the claim that our Big Bang occurred finitely long ago). For the perspective of someone much better-informed about this issue than I am, see this link .

For the record, I'm far from happy with Krauss's way of putting things, which is why in my response I linked not to Krauss's book but to Albert's (scathing) review of it, the same review later linked to by Professor Stairs.

Thanks for the chance to clarify my answer to Question 25338 . I can see how my answer might have given the wrong impression. I didn't mean to suggest that, whatever one's desired conclusion, one can always find less controversial premises that imply it. That is, one may fail in the attempt to improve one's argument, no matter how hard one tries. One's conclusion may just not follow from less controversial premises. My point was simply that a logically valid argument from less controversial premises to conclusion X is better than a logically valid argument from more controversial premises to conclusion X. It's something one should strive to find, even though there's no guarantee of success, and failing to find it may be a good reason to reconsider one's conclusion.

Interesting question! First, I should note that some philosophers object to the claim that the ordinary term "water" refers to the chemical kind H2O. See here and here . Just for simplicity, my answer will ignore their objections. Second, a point about form. Using italics for propositions, I think we should replace the proposition Water is H2O with the universally quantified proposition Whatever is water is H2O , because, as I see it, the first proposition is false in all those possible worlds in which water doesn't exist, whereas the second proposition is (vacuously) true even in such worlds. Likewise, as I see it, the proposition Pegasus is Pegasus is contingently false (there being, as a matter of contingent fact, no such thing as Pegasus), whereas Whatever is Pegasus is Pegasus is necessarily true. So, on this view, the law of identity has the form "Whatever is A is A." I'd say that the important difference between Whatever is water is H2O and Whatever is A is A isn't...

The reclusive behavior you describe will be familiar to many philosophers! The great Scottish philosopher David Hume (1711-1776) famously wrote that socializing with friends helped him escape from his philosophical brooding when he felt overwhelmed by it. But thank goodness for his philosophical brooding! Otherwise he'd have been a much less important contributor to human civilization. You've asked a psychological question, really, so I'm not equipped to answer it, but the list of philosophers who have preferred thinking over socializing is long and illustrious. I'd recommend that you look for psychological literature that discusses the personality traits of introversion and extroversion and their characteristics. If you should discover that extroverts typically "have less interest in learning things" or believe "they already know or understand all that they ever wondered about," then how sad for them. Keep inquiring!

Your question raises a number of philosophical and scientific issues. You'll find them expertly discussed in this short and reasonably priced book by Alfred R. Mele, one of the world's leading authorities on the topic: https://global.oup.com/academic/product/free-9780199371624. Enjoy.

It's hard to see how any thought experiment could be good for filtering out all intuition-based arguments, for the simple reason that one's reaction to any thought experiment is itself a matter of one's intuitions. In your own thought experiment, I'm supposed to imagine how I'd react to the utility-monster objection if two non-actual conditions held: (1) I'm an alien, and (2) I'm born with the intuition that utilitarianism is self-evident. To be honest, I have no idea how I'd react under those conditions, but the only thing I can consult to answer the question would be my intuitions about the imagined case. Any (finitely long) argument, including any sound argument, will rely on intuitions in the sense that it will contain premises that the argument simply asserts and doesn't defend. That being said, if one's argument depends on controversial premises, then one ought to improve the argument by finding less controversial premises that imply one's conclusion.

I agree. I don't know what Berkeley says about whether any nonhuman animals possess minds, but on his view, I take it, nonhuman animals would need to possess minds in order to perceive anything. Indeed, according to Berkeley, not only does the tree make no sound unless a mind perceives the sound, but the tree doesn't even exist without a mind to perceive it. (Even if no finite mind perceives the tree, Berkeley attributes the tree's existence to the tree's being perceived by God's mind.) Notice, too, that if we construe "a sound" dispositionally, i.e., as simply a disturbance that would be heard if there were a normally equipped listener to hear it, then sounds can occur even with no listeners (human or nonhuman) on the scene.

I think so. Consider the example you gave. A's selflessness (her generosity, anyway) is manifested by her sending the money to B, whether or not B ends up accepting the money. Now, if A somehow knows that B will return the money immediately and is counting on B to return it, then A's selflessness is only apparent rather than genuine. But otherwise, I see no reason why A's action can't be considered genuinely selfless, whether or not the recipient in fact keeps the money. Further, I see no reason why C must be deemed selfish just because he accepts the money: it might be that, through no fault of his own, C desperately needs the money. What I think genuine selflessness does require is scarcity: if a particular resource is available to all in unlimited supply, then no one can genuinely make a gift of that resource, let alone a selfless gift. So I don't think there can be selflessness in heaven, if heaven is as it's described by various religions.

Not unless ethical egoism is true. See more at the link.