I am reading a by book by the great logician Raymond Smullyan. In this book he says that any statement of the form, "All As are Bs" are true if there are no "As". That is, these statements are vacuously true. He gives the following example, "All Unicorns have 5 legs" is true since there are no unicorns. So is "All unicorns have 6 legs", and "All unicorns are purple", etc. But this strikes me as obviously false. For example, "All unicorns have two horns" and "All unicorns are necessarily existing" are false statements. The first is false in virtue of the fact that unicorns are by definition one-horned. The second is false in virtue by the fact that it is impossible for something to be both necessarily existing and nonexistent. Am I missing something here or misreading Smullyan? Or are these counterexamples sufficient in refuting the claim that any statement of the form "All As are Bs" is vacuously true if there are no "As"? For reference the book is, "Logical Labyrinths" from pages 99-101. Thanks...

I don't know that book in

I don't know that book in particular, but I can give you a standard explanation that at least makes sense of the view you find puzzling. In Aristotle's logic, any statement of the form "All S are P" implies that at least one S is P, so the statement comes out false (rather than vacuously true) if nothing is S. By contrast, in contemporary logic, "All S are P" is interpreted as saying "For anything at all, if it is S, then it is P": it is interpreted as a universal quantification applied to a conditional statement. Crucially, the conditional statement "If it is S, then it is P" is standardly treated as a truth-functional conditional that is equivalent to the disjunction "It is not S, or it is P." Now suppose that nothing is S, so that "It is not S" is true of everything. Then the disjunction "It is not S, or it is P" will come out true no matter what we substitute for "it," because a true disjunction needs only one true disjunct. In that case, the truth-functional conditionals "If it is S, then it...

You can't create something out of nothing can you! And yet, here we exist. Is this not the most relevant question we can't answer?

@ Jonathan: If I may, I think

@ Jonathan: If I may, I think Leibniz's analogy is faulty. The constraints on what counts as a good explanation of why there have been any books at all (or any books bearing a particular title) need not be constraints on what counts as a good explanation of why there have been any states of the universe at all. I try to explain why in this brief article .

What is in myself and not in others and it doesn't change from childhood to death

Besides your identity? Or are you seeking an analysis of personal or bodily identity? If the latter, then I recommend starting here , here , and here .

Is there any way to escape an endless loop of "why"? Like when I was a kid I constantly asked my parents how something works and then it went to why something works. After they responded then it went to another why that went deeper and so on and so on. Similarily we can endlessly ask 'why' on matters like oughts of with what hand should I hold fork or on which hand should I wear a watch etc. So is there a way to escape it? Something like fact about ourselves comes to mind (i.e. because I want to do so) but that seems trivial or problematic in some areas (morality).

With matters of custom, such

With matters of etiquette, such as which hand to use for the fork, or matters of personal preference, such as which wrist to use for one's watch, I don't think "Why?" questions are intellectually substantial enough to be worth asking more than once or twice. But philosophical and scientific questions are intellectually much more substantial, much deeper. There it makes excellent sense to keep asking "Why?" questions for as long as those questions remain well-posed. You're right that we don't want a loop -- a circle -- of "Why?" questions, because in that case a question reappears after it has already been adequately answered. But a loop is different from a regress of questions, which may be finitely long or indefinitely long. On whether an indefinitely long regress is always something to avoid, see this SEP entry .

I am having trouble understanding how the idea of qualia and p-zombies is logically coherent. If philosophical zombies are conceivable, and behave exactly the same as human beings, then zombies would also claim that they possess conscious experience / qualia, even though they do not. Doesn't it then follow that our conviction that we have qualia cannot be DUE to us actually having qualia, since zombies would hold the same conviction? Thanks.

No, it doesn't follow.

No, it doesn't follow. Compare: If an evil demon were thoroughly deceiving me right now about my surroundings, then my current perceptual experience would -- unbeknownst to me -- be unreliable. But the truth of that conditional doesn't imply that my current perceptual experience is -- unbeknownst to me -- unreliable. Likewise, if zombies are possible, and if they claim that they have conscious experience, then it follows that claiming to have conscious experience doesn't imply having conscious experience. But we knew that already.

Recently I read a comment on an online debating site where someone stated “ Every deductive statement regarding the real world relies on induction” to me that does not sound correct am I missing something?

One reason it doesn't sound

One reason it doesn't sound right to me is that I don't know what could be meant by a "deductive statement." I know what a deductive argument is, but it always contains more than one token statement. Did the site say, instead, "every declarative statement" (i.e., every declarative sentence)? In any case, consider the statement "There are no colorless red cars." It's a declarative statement. Does it regard the real world? Arguably, yes: it's at least partly about cars. But knowing its truth doesn't require induction -- it's analytically true. On the other hand, maybe despite appearances it's not a statement even partly about cars but only about the logic of the concepts red and color . We'd need an agreed-on criterion of "aboutness" in order to decide.

My friends and I have gotten into an argument over whether or not there is/are opposites to a circle. Both sides have some valid points, but the main idea is whether or not there are opposite shapes.

I can't think of any ordinary

I can't think of any ordinary sense of "opposite" that allows for the existence of opposite shapes (i.e., closed plane figures). But you and your friends could invent a technical sense of "opposite" that allows for opposite shapes. Maybe the opposite of a shape is the mirror image of the shape along the vertical axis, or along the horizontal axis, or along some oblique axis, provided that opposite shapes never look the same. On that definition, a circle wouldn't have an opposite shape, but a triangle could. In any case, there's nothing to disagree about until you have a suitably precise definition of "opposite shape," which again I think you'll have to stipulate, because ordinary language doesn't supply one.