This is the table of contents and first chapter of Physics Meets Philosophy at the Planck Scale (Cambridge University Press, 2001), edited by Craig Callender and Nick Huggett. The chapter discusses the question of why there should be a theory of quantum gravity. We tackle arguments that purport to show that the gravitational field *must* be quantized. We then introduce various programs in quantum gravity and discuss areas where quantum gravity and philosophy seem to have something to say to each (...) other. (shrink)

Almost everything that we know about Zeno of Elea is to be found in the opening pages of Plato's Parmenides. There we learn that Zeno was nearly 40 years old when Socrates was a young man, say 20. Since Socrates was born in 469 BC we can estimate a birth date for Zeno around 490 BC. Beyond this, really all we know is that he was close to Parmenides (Plato reports the gossip that they were lovers when Zeno was young), (...) and that he wrote a book of paradoxes defending Parmenides' philosophy. Sadly this book has not survived, and what we know of his arguments is second-hand, principally through Aristotle and his commentators (here I have drawn particularly on Simplicius, who, though writing a thousand years after Zeno, apparently possessed at least some of his book). There were apparently 40 ‘paradoxes of plurality’, attempting to show that ontological pluralism — a belief in the existence of many things rather than only one — leads to absurd conclusions; of these paradoxes only two definitely survive, though a third argument can probably be attributed to Zeno. Aristotle speaks of a further four arguments against motion (and by extension change generally), all of which he gives and attempts to refute. In addition Aristotle attributes two other paradoxes to Zeno. Sadly again, almost none of these paradoxes are quoted in Zeno's original words by their various commentators, but in paraphrase. (shrink)

This item is a chapter from a book in progress, entitled "True Motion". Leibniz’s mechanics was, as we shall see, a theory of elastic collisions, not formulated like Huygens’ in terms of rules explicitly covering every possible combination of relative masses and velocities, but in terms of three conservation principles, including (effectively) the conservation of momentum and kinetic energy. That is, he proposed what we now call (ironically enough) ‘Newtonian’ (or ‘classical’) elastic collision theory. While such a theory is, for (...) instance, vital to the foundations of the kinetic theory of gases, it is not applicable to systems – like gravitational systems – in which fields of force are present. Thus, Leibniz’s mechanical principles never led to developments of the order of Newton’s in the Principia (additionally, he hamstrung their application by embedding them in a baroque philosophical system). (shrink)

Where should we begin our story? Many books start with Newton, but Newton was responding to both Galileo1 and especially (for our purposes) Descartes. But Galileo and Descartes themselves were writing in the context of late Aristotelianism, and so were trained in and critical of that rich school of thought, so if we want to fully understand their work we would need to understand scholastic views on space and motion (see Grant, 1974, Murdoch and Sylla, 1978 and Ariew and Gabbey, (...) 1998). But late scholasticism itself is the result of a long history tracing from Plato and Aristotle through Jewish, Arabic, Islamic and European thought. And of course Plato and Aristotle are explicitly reacting to their predecessors and contemporaries. In other words, we could start the story as early in recorded thought as we like. (shrink)