William Lane Craig - christelijke apologeet en debater

quote:

Op zaterdag 26 september 2009 11:01 schreef Papierversnipperaar het volgende:

[..]

Als je voor (de oorsprong van) God andere standaards gebruikt ben je hypocriet.

quote:

Op zaterdag 26 september 2009 11:08 schreef Haushofer het volgende:

[..]

Nee, dan is het hek van de dam.

quote:

Op zaterdag 26 september 2009 11:22 schreef Haushofer het volgende:

[..]

Maar dat probeert iemand als Craig toch juist te doen? De opstanding van Jezus probeert hij krampachtig "historisch aannemelijk te maken" door te beargumenteren dat alle alternatieven onwaarschijnlijk zijn, er moet een schepper achter dit universum zitten door een causaliteitsargumentatie die voor mijn gevoel al decennialang geen hout meer snijdt etc.

Het is in mijn ogen het typische "ik wil graag geloven, en ik zal het intellectueel aannemelijk maken ook!". Als mensen niet zo verdraaid bijgelovig en irrationeel waren geweest had ik geloofd dat dit soort standpunten een tussenfase zijn waarbij het eindstation er een is van erkenning dat dit soort rare vermenging van ratio en religieus denken geen hout snijdt.

quote:

Op zaterdag 26 september 2009 11:32 schreef Haushofer het volgende:
Misschien denk ik te fysisch. Laat ik het es anders formuleren:

Kan iemand een formulering geven van het begrip "causaliteit" wat op de een of andere manier fundamenteler is dan de natuurkundige definitie? Als causaliteit echt een eigenschap is van het universum wat de fysische wereld en de ruimtetijd overstijgt, dan kun je Craig's redenatie al een stuk serieuzer nemen.

Heeft causaliteit een betekenis als je de natuurkundige definitie loslaat?

quote:

Op zaterdag 26 september 2009 12:11 schreef Haushofer het volgende:

[..]

Nee. Causaliteit is gebaseerd in termen van eigenschappen van ruimtetijd, en heeft betrekking op datgene wat zich in die ruimtetijd bevindt. Ruimtetijd is niet gelijk aan datgene wat er in zit. Hetzelfde zie je bijvoorbeeld bij het volgende voorbeeld: informatie (of simpeler: objecten) kunnen niet sneller dan het licht, maar ruimtetijd kan zich prima zo snel uitzetten dat objecten een onderlinge snelheid verkrijgen groter dan de lichtsnelheid! Waarom? Omdat ruimtetijd volgens de ART niet hetzelfde is als datgene wat zich er in bevindt.

Hoe ruimtetijd ontstaat? Dat weten we niet, want de ART is niet meer geldig zodra het om singulariteiten gaat. Ik heb al verscheidene Christenen meegemaakt die dit als ontkenning van het probleem zien, maar het cruciale punt hier is (en daarom gebruik ik dikgedrukte letters): Zonder theorie van quantumgravitatie kunnen we werkelijk niks zinnigs zeggen over wat de oorsprong is van ruimtetijd. Craig gaat, zover ik kan zien, volledig voorbij aan dit cruciale punt (of ik lees er over heen; als je een link hebt, graag).

quote:

The standard model does not - indeed, cannot - explain why the Big Bang occurred, but it can predict that it occured. So the question reduces to whether we have good evidence for this prediction of the standard model. The Hawking-Penrose singularity theormes governing objects in gravitational self-collapse render such an initial cosmological singularity inevitable so long as the equations of classical Geneeral Relativity apply. Some theorists have hoped to avert the initial singularity by the introduction of a quantum theory of gravitation. But even on quantum gravitational cosmological models, such as the Hartle-Hawking model, while the singular beginnning point is smoothed away, the prediction of a finite past and an absolute beginning of the universe remains unaltered, so that, in Hawking's words, the universe 'would quite litterally be created out of nothing'. Thus, Barrow comments, 'This type of quantum universe has not always existed; it comes into being, just as the classical cosmologies could, but it does not start at a Big Bang where physical quantities are infinite...."

quote:

Now it is certainly true that theorists prefer a theory which involves no singularities, since the laws of physics break down at such a point; but that heuristic does nothing to rule out the fact that the correct theory of the universe may well involve singularities. The Hawking-Penrose singularity theorem proves that so long as the General Theory of Relativity holds, an initial cosmological singularity is inevitable. A singular beginning of the universe is not ipso facto unphysical or unscientific, though it may be discomfiting. A theorist is always at liberty, if he has an aversion to singularities, to "cut out" the initial singular point from the model, treating it, in Fitzgerald's words, "as a kind of mathematical limit lacking physical reality."{31} But the discomfiture of an absolute beginning remains unabated. As cosmologist Andrei Linde candidly confesses, "The most difficult aspect of this problem is not the existence of the singularity itself, but the question of what was before the singularity . . . . This problem lies somewhere at the boundary between physics and metaphysics."{32}

Taylor errs in inferring that the presence of an initial cosmological singularity implies an era about which the standard model's predictions are unreliable. The singular state is a durationless point with respect to time, the analogue to a temporal instant; t=0 does not even lie within the history of the universe, much less constitute an era, but lies on the boundary of space-time. Taylor seems to have confused the singular state with the Planck era prior to 10-43 sec after the Big Bang, whose description requires the marriage of GTR and quantum theory to yield a quantum theory of gravitation.{33} Some theorists hope that such a theory will not involve the singularities inevitable in classical gravitation; but this hope may well prove vain. John Barrow has rightly cautioned that "one should be wary of the fact that many of the studies of quantum cosmology are motivated by the desire to avoid an initial singularity of infinite density, so they tend to focus on quantum cosmologies that avoid a singularity at the expense of those that might contain one."{34} Noting the same tendency, Roger Penrose states, "I have gradually come around to the view that it is actually misguided to ask that the space-time singularities of classical relativity should disappear when standard techniques of quantum (field) theory are applied to them."{35} For if the initial cosmological singularity is removed, then "we should have lost what seems to me to be the best chance we have of explaining the mystery of the second law of thermodynamics."{36} What Penrose has in mind is the remarkable fact that as one goes back in time the entropy of the universe steadily decreases. Just how unusual this is can be demonstrated by means of the Bekenstein-Hawking formula for the entropy of a stationary black hole. The total observed entropy of the universe is 1088. Since there are around 1080 baryons in the universe, the observed entropy per baryon must be regarded as extremely small. By contrast in a collapsing universe the entropy would be 10123 near the end. Comparison of these two numbers reveals how absurdly small 1088 is compared to what it might have been. Thus, the structure of the Big Bang must have been severely constrained in order that thermodynamics as we know it should have arisen. So how is this special initial condition to be explained? According to Penrose, we need the initial cosmological singularity, conjoined with the Weyl Curvature Hypothesis, according to which initial singularities (as opposed to final singularities) must have vanishing Weyl curvature.{37} In standard models, the Big Bang does possess vanishing Weyl curvature. The geometrical constraints on the initial geometry have the effect of producing a state of very low entropy. So the entropy in the gravitational field starts at zero at the Big Bang and gradually increases through gravitational clumping. The Weyl Curvature Hypothesis thus has the time asymmetric character necessary to explain the second law. Without the initial singularity we should have white holes spewing out material, in contradiction to the Weyl Curvature Hypothesis, the Second Law of Thermodynamics, and probably also observation.{38} Penrose supplies the following figure to illustrate the difference:

If we remove the initial cosmological singularity, we render the Weyl Curvature Hypothesis irrelevant and "we should be back where we were in our attempts to understand the origin of the second law."{39} Could the special initial geometry have arisen sheerly by chance in the absence of a cosmic singularity? Penrose's answer is decisive: "Had there not been any constraining principles (such as the Weyl curvature hypothesis) the Bekenstein-Hawking formula would tell as that the probability of such a 'special' geometry arising by chance is at least as small as about one part in 101000B(3/2) where B is the present baryon number of the universe [~1080]."{40} Thus Penrose calculates that, aiming at a manifold whose points represent the various possible initial configurations of the universe, "the accuracy of the Creator's aim" would have to have been one part in 1010(123) in order for our universe to exist.{41} He comments, "I cannot even recall seeing anything else in physics whose accuracy is known to approach, even remotely, a figure like one part in 1010 (123)."{42}

Furthermore, the fact that certain quantum gravity models like the Hartle-Hawking model lack an initial singular point is in any case really quite irrelevant to our concern, since such models still posit the finitude of the past and an origination of the universe ex nihilo. As Barrow explains, "This type of quantum universe has not always existed; it comes into being just as the classical cosmologies could, but it does not start at a Big Bang where physical quantities are infinite . . . ."{43} The Hartle-Hawking universe thus gives "a picture of 'creation out of nothing'," even though "one never runs into an unusual point like the apex of a cone."{44}