The Bible tells us all sorts of things -- e.g. that wheat ripens later than barley (Exodus 9:31-33). Now, when farmers arrange their work so the barley gets harvested first, then I suppose you might say that they are acting according to what the Bible says about crops. But of course, they don't arrange their work thus and so because the Bible says wheat ripens later, but because it actually does ripen later. The Bible also tells us that we should help each other out -- for example "If you see your brother's donkey or his ox fallen on the road, do not ignore it. Help him get it to its feet." (Deut: 22:4). Now, again, when I stop to help a broken-down motorist on a country road, for example, I suppose you might say that I am acting according to what the Bible enjoins. But I don't act that way because the Bible says that it is the decent thing to do, but because it actually is the decent thing to do. (After all, there are plenty of things the Bible enjoins that I don't think decent at...

Two comments on the central pair of assertions: "[T]houghts are not physical. They're metaphysical" -- one terminological (but not insignificant), the other more substantial. (1) The terminological comment is this: "Metaphysical" does not mean "non-physical", "supernatural", or anything of that kind. Metaphysics is just the traditional label for a bunch of topics famously discussed -- though not for the first time! -- in Aristotle's Metaphysics . That book, or rather collection of books, is so called because it was placed meta ta phusika , after the Physics , by ancient editors. Its topics include questions like what makes something an object rather than an event or process? must objects have essential properties and if so what? are numbers a kind of object? what is a cause? Now, those questions (and similar ones that we also nowadays by extension call metaphysical) raise very general issues. And you can see why the ancients might have been at a bit of a loss as to how to...

I guess that different philosophers adopt somewhat different usages here (it's one of those cases where you have to glean from someone's writings their preferred usage). It will be interesting to see what colleagues say. But speaking for myself, I think I use the word in two different ways. (A) First, on my lips, since it's true that (1) Barack is tall, I'd be on for saying (2) Barack instantiates the property of being tall. Now, I treat properties as worldly items (part of the furniture of the world, so to speak), while concepts are ways of thinking of properties. In Fregean jargon: properties are in the realm of reference (what we think about), concepts are in the realm of sense (constituents of the thoughts we have about what objects have which properties). So, at least when I'm on my best behaviour, I'd not be too happy to say (3) Barack instantiates the concept tall since the relation that Barack (the man) has to tallness (the property) is different in...

There is a number of issues raised here. Let me make just two points. First, on the specific idea that "perhaps what we think is universally true is not, we’resimply programmed to think it is? ... that’d be a profoundlyeffective evolutionary tool for preservation of the species." But of course, if we were programmed to believe falsehoods , that would not in general promote survival. To get food, for example, we basically need true beliefs about where it is to be found. Of course, this isn't to say that we need always get things right: it might be that evolution has provided us with quick-and-dirty information processing capacities that deliver true beliefs often enough to promote survival. But the point remains that what promotes survival is a sufficient number of true beliefs. So the thought that our beliefs are generated by mechanisms provided by our evolutionary history cannot by itself be a reason for across-the-board distrust. Secondly and more generally, why should we...

It is a requirement for something to be genuinely known to be true that it is true. So knowledge implies truth (in the sense that if X knows that so-and-so, then it is the case that so-and-so). But that doesn't make knowledge the same as truth. The implication the other way around doesn't hold. There are truths that you don't know, that I don't know, and indeed that no one right now knows (maybe because nobody has bothered to find them out, maybe because the time has past when anyone could check, or because the truths are about far-off events like meteorite strikes on the far side of the moon, or for other kinds of reason). Leaving ominiscient deities out of it, not every truth is known. But we might wonder whether every truth is knowable , in principle, e.g. by a suitably placed and sufficiently smart observer. The trouble with that idea is in spelling out the "in principle".

You need to distinguish the claim that mathematics is grounded on logic, and the claim that mathematics uses logic. The weaker second claim is evidently true, at least in this sense. Mathematical reasoning is a paradigm of good deductive reasoning. And standard systems of logic explicitly aim to codify, more or less directly, the kinds of good deductive reasonings that mathematicians use. (And computers might be used to echo some such reasonings too.) But the fact that mathematics uses logical reasoning doesn't show that mathematics is grounded on logic if that is the much stronger thesis that at least arithmetic, maybe the whole of classical analysis, just follows from pure logic plus definitions of mathematical notions in logical terms. (I take it that it is this logicist thesis which you are thinking of, when you say that there are "serious problems" about the idea that mathematics is grounded on logic). For example, you might think that in set theory we use logic to...

An interesting question. Of course, our neuroscientist has learnt something about love, for she has learnt something about the neural causes of certain feelings bound up with love. But you might well feel that there is a sense in which her discoveries don't help us understand what really matters about love as part of human life (hasn't in the important sense learnt about the nature of love). That needs a quite different sort of enquiry, pursued by poets and playwrights and novelists down the ages. Compare: someone who tells us about the chemical composition of the pigments used in Botticelli's Primavera has told us something about the painting. But again such discoveries don't help us understand the painting in the way that matters, as a work of art, as part of the human world: understanding that requires something quite different from chemistry. We could stop there. But perhaps there is a bit more that needs to be said. For there can remain a nagging feeling that the neuroscientist...

It's worth saying something first about Descartes (as it wasn't his view that he couldn't prove he wasn't dreaming). Descartes is troubled that, as he sees it, the then dominant systematic story of the world is in deep error, and is getting in the way of the growth of the revolutionary new science of the day. He has a diagnosis, too, of the source of error -- he sees Aristotelianism as springing from some deeply embedded childhood habits of thought. Radical measures are required to prise us out of such deep-rooted error. The ‘Method of Doubt’ provides the once-in-a-lifetime jolt needed to shift us out of certain childish thought-habits and to get us adopt better intellectual methods and open the way to improved science. Faced with even the most reasonable-seeming presumptions, Descartes suggests, "I must withhold my assent from these former beliefs just as carefully as I would from obvious falsehoods, if I want to discover any certainty in the sciences." So for Descartes, it is not that our...

There is in fact a tradition of 'constructivist' mathematics which does not endorse the law of excluded middle. Very roughly, suppose you think that mathematical truth consists in the possibility of a constructing a proof. Then there is no reason to suppose that, inevitably, either P or not-P -- because there is no reason to suppose that (for each and every P) there is a possibility of proving P or is a possibility of disproving P. To find out more about this, you can read (at least the opening couple of sections of) this article . Note, however, that refusing to endorse the law of excluded middle for mathematical propositions is not to deny the law, nor is it to assert that there is a "third state" between truth and falsehood. Still, for certain other purposes, it can be useful to explore three-valued logical systems (even multi-valued logics), which allow more "states" that the classical true/false pair. From the same source, here's another article -- note the section on ...

One thing I know is the difference between the taste of sangiovese and pinot nero -- a bit of wine-wisdom I've acquired over the years. But I certainly would be very hard put to express that knowledge in propositional form, at least in any informative way that could usefully convey my knowledge to you. Is there any proposition I could use to do that? Of course, I can say -- taking a sip -- " this one is sangiovese", and -- taking another sip -- " that one is pinot nero". But that won't help you, unless you are sipping away from the same wines, and you are attending to the differences. You need to experience the wines for yourself, and need to pay attention to them and learn to tell them apart. And developing that skill, that know- how , seems to require something other than picking up propositional knowledge- that about the wines.