You won't be surprised to learn that what these terms mean is a matter of some controversy among scholars. Some bits, however, have achieved general agreement. Pyrrhonian and Academic skepticism mark two branches of ancient skepticism. David Hume and other moderns also used the terms. One way to discriminate them is institutionally. Not long after Plato's death his school just outside of Athens, the Academy, became dominated by skeptical thinkers. The philosophical work engaged by those thinkers came, of course, to be called Academic skepticism. The major texts by which Academic skepticism, however, came to be known to the modern world were not those of philosophers leading the Academy but, rather, of the Roman philosopher, Cicero. His books, Academica and De natura deorum , became highly influential. Pyrrhonian skepticism, by contrast, follows a line rooted in the thought of a man named Pyrrho, who lived in small town of Elis, on the other side of Greece. Pyrrho was not associated with a...

Briefly, yeah. I think I see what you're getting at. When P and Q are true (which I think is what you mean by 'P&Q'), then P->Q, Q->P, and P is materially equivalent to Q. But note that this was the case for your earlier puzzle, too. Keep in mind that in standard first-order propositional logic, P->Q is a matter of only "material" implication, and P equivalent to Q is a matter only of "material" equivalence. That is, all 'P->Q' says is that when P is true Q is also true. All the equivalence says is that they have the same truth values. It doesn't say that there's some reason for the truth values being as they are, that there's any other connection between the statements, or that P and Q will be true in every possible or imaginary world. In our world P and Q happen both to be true, and that's enough. The issue you're pointing to is addressed by what's come to be called "Relevance Logic" and it is sometimes used to mark a difference in the use of the terms "implication" and "entailment." In relevance...

Or, more generally, "Why do philosophers ask such absurd questions?" The basic issue here is what philosophers have come to call the "Principle of Sufficient" reason. You might say, in the simplest terms, if it doesn't distort things too much, that the principle maintains that there must always be a reason--for each event, for the existence of each thing, and for everything as a whole. That might seem obvious, but some philosophers (David Hume, for example) have disagreed, holding that that there's nothing non-sensical in holding that things might just happen or pop into existence for no reason at all. Anyway, the question of why there is "something rather than nothing" might be understood as exploring the principle at its limit. It's pretty clear, for many, why baby's come to exist and why there are iPhones. But why does anything exist? Why does the universe exist at all? Is there an answer to that question? If not, perhaps the Principle of Sufficient reason does not really hold, or, anyway, holds only...

Well, yes and no. What you've got here is a tangle, just the sort of tangle that actually does lead to serious philosophical problems. You see, what you've got in the first place isn't exactly a syllogism. So, it's neither a valid nor an invalid syllogism. It looks a lot like the following syllogistic form (which is invalid): "All P are M. All S are M. Therefore, All S are P." You can see that this invalid by plugging in the following terms. "All Pigs are Mammals. All Siberian Huskies are Mammals. Therefore, all Siberian Huskies are Pigs." While the two premises are true, the conclusion is clearly false--and that doesn't happen in valid arguments. This invalid form doesn't have a specific name, really, but it does commit the fallacy of "undistributed middle." I think one reason you may have lost your way here is because you use equal signs in your presentation. If you intend to use the equal sign as short hand for the verb "to be" ("are") in the same what as I have used "to be" ("are") in my example,...

I guess I think that the most important thing would be for philosophy to be taught more widely. I think it a scandal, for example, that logic isn't required in every school--primary, middle, high school, and university--across the country. How is it that we've come to require geometry but not basic logic? Training in ethics, political philosophy, and the history of philosophy ought to be widespread. Philosophers ought also to be sought out to serve as advisers for political leaders, and philosophical training ought to be more highly regarded as a credential for hiring people into positions of leadership. You may know that already insurance companies and hospitals commonly employ medical ethicists in making policy decisions. We need more of that. Philosophers ought to be more deeply engaged in public discourses. More newspaper columns, tv commentators, and popular writers ought to be philosophers.

Gosh, wouldn't it be great if everyone were a metaphysician? Unfortunately, using ideas that metaphysicians explore no more makes one a metaphysician than using using religious concepts makes one a theologian. There's no simple definition of "metaphysics," but as a serviceable start one might say that metaphysics is that branch of philosophy that investigates the most fundamental and the most general features of reality or what we think about reality. So, for example, while a historian might ask, "What were the causes of the Crimean War?" A metaphysician might ask, "What is history, what is time and history, what are historical causes, and what are human agents such that they can engage in war?" While a biochemist might ask, "What are the compounds that cause a specific reaction in the intestines?" A metaphysician might ask, "What is 'Being' generally, and what is causation generally?" While someone might ask whether or not she should return a wallet she's found on the ground, a metaphysician might ask...

I think I see what you mean. But if I do, then the phrase "arbitrary for humans" is not exactly the way to pose your question. Humans aren't really making the choice in your scenario. So, the choice is neither arbitrary nor non-arbitrary for them. I think you might rather mean something like: Would God's arbitrarily commanding any conduct provide sufficient grounds for humans to regard that conduct as good? My sense is that the qualities of a lot of religious faith lead people to answer in the affirmative. In particular, for the faithful it's likely to be almost inconceivable to defy God's command on grounds that what's commanded seems immoral from a merely human point of view. The story of Abraham and Isaac exemplifies just this sort tendency in faith. The problem is that it seems to many at least as intolerable to accept that stealing, rape, mass murder, etc. could ever be acceptable. For example, many will find it intolerable to honor a command to torture, molest, mutilate, and kill innocent children-...

Yeah, I think that's right. The theistic hypothesis is not testable through the procedures of natural science. That in itself has led many, myself included, to a kind of agnosticism about theism. That's also one of the reasons why neither creationism nor much of what is described as intelligent design are scientific. Do note, however, that testability may not be the only basis for rejecting (or accepting) theism. Some reject theism because they find theistic language itself intolerably confused and senseless. Others point to the political and moral problems associated with theisms (the violence, the intolerance, the blunting of norms of reason and critical thinking). (I frequently find that line of reasoning attractive.) Some object to the way theism fails to produce agreement and generates divisions and sects. (Often compelling to me, too.) Along similar lines, others have concluded that it's simply undesirable to commit to beliefs that are excessively complex or, alternatively not as simple as...

Given the way many in the wealthy parts of the world live, this is a compelling question. I think, however, that as posed the answer must be "no." For one thing, the best paying jobs may sometimes contribute more bads than goods to the world. For example, in some circumstances criminal activity or highly polluting industry may offer the best paying job. Also, it is not morally obligatory to live off as little as one can manage, giving away the rest to charity. People have obligations to themselves as well as to others, and one must balance what one owes to others against what one owes oneself. Finally, it's important to understand that some acts are morally admirable without being morally obligatory; and from where I sit extraordinary self-sacrifice for the sake of charity to others counts as just such an act. Having said that, it remains true, I think, as a matter of judgment, that many people in wealthier parts of the world live in ways that have tipped the balance excessively in the direction of...

No and yes. Historically, the idea of toleration developed along side streams of philosophical scrutiny of religious belief that suggested, rightly I think, that there's just not very good reason for zealous commitment to religious beliefs. So, while a zealot may, as you describe it, be exceedingly confident or dogmatic in his or her belief, there's no sound justification for doing so. In this sense, strains of modern skepticism have tempered religious belief in the form of what early modern thinkers called "enthusiasm." But, on the other hand, there are many ways of holding a belief "strongly." There are, one might say, ways of holding religious beliefs strongly that are consistent with tolerance and ways of holding beliefs strongly that are inconsistent. Tolerance itself commonly suggests that contrary views are considered wrong and even, perhaps, obnoxious. So, analogously, we speak of a body's capacity to tolerate a toxin or to tolerate the cold, etc. So, just as we might speak of a person who...