I'm reminded of a famous remark from the economist, John Maynard Keynes. On once being accused of inconsistency -- what I believe the Americans like to call 'flip-flopping' -- he replied: "When the facts change, I change my mind. What do you do, sir?" I don't think any philosophers would wish to insist that one's ethical behaviour and philosophy must always remain consistent over time . In terms of individual actions, when the situations are not identical, it might well be absolutely appropriate to behave in different ways. And even in terms of more general ethical principles, it's entirely right and proper for us to reassess and potentially revise these in response to changes in the world or even just changes in ourselves. The kind of consistency that I think philosophers would, however, wish to insist upon is consistency at a particular time, or within a particular situation. If one maintains as a general rule that nobody, oneself included, ought to do X, and yet still goes ahead and does X...

I hadn't originally intended to attempt a reply to this one, simply because the history of this is something that I've never really looked at in detail. But I do have to take issue with something that Allen Stairs says: "The distinction between deduction and induction never was a distinction between universal-to-particular and particular-to-universal." Erm... that's precisely what it was. I've had a quick leaf through a few of the books I happen to have to hand, and it's quite clear that this was how folks like Bacon, Arnauld & Nicole, Leibniz, Newton, Berkeley, and many others, understood the distinction. Not to mention Aristotle. Or how about the following from John Stuart Mill's 1843 work, A System of Logic, Ratiocinative and Inductive : "Although, therefore, all processes of thought in which the ultimate premises are particulars, whether we conclude from particulars to a general formula, or from particulars to other particulars according to that formula, are equally Inductive; we...

Well, it all depends on what you're hoping to get out of it. If your interest is in the history of philosophy, and you want to find out about the state of logic and philosophy in nineteenth-century Britain, then sure, go ahead and read it. (Although, given a choice, I'd actually recommend John Stuart Mill's System of Logic over Whateley). But if your interest is in logic as such, and you're hoping that this book will give you a decent introduction to the subject and a general overview of the state of play, then no, it really, really won't do that. Logic didn't actually change a whole lot from Aristotle's time right up until that of Whateley and Mill: but then, just a few decades later, it suddenly underwent a radical transformation. The work of Gottlob Frege, Bertrand Russell and others, in the late nineteenth and early twentieth centuries, completely revolutionised the subject, and works written before their time are nowadays of interest only to historians. That's not to say that I'd...

In his paper, 'The Ways of Paradox', W. vO. Quine draws up a useful classificatory scheme for paradoxes, dividing them up into three groups. 'Veridical paradoxes' are conclusions that seem profoundly counter-intuitive, and yet are actually perfectly sound. An example might be the paradox of the ravens: on the face of it, it doesn't seem right to claim that an observation of a red pencil can lend any support at all to the hypothesis that all ravens are black, but there's a good argument to suggest that actually it does lend a (very) small amount. (Basically, the hypothesis that all ravens are black is logically equivalent to the hypothesis that all non-black things are non-ravens, and the appropriate method of confirmation for the hypothesis in that latter formulation would seem to be to take a non-black thing and to check whether it's not a raven). 'Falsidical paradoxes' are ones where an absurd conclusion seems, on the face of it, to be supported by a good argument, but where further scrutiny can...