stunney: what is your evidence the universe could have been different than it is?

Lots of virtual universes have been modelled on computers. Most of them are incompatible with life. That's why atheists are rationally compelled to posit a multiverse.

What is the sampling space of universes?

See previous reply.

Utter speculation without any scientific content.

Completely, demonstrably false. See previous.

But funny anyway, keep up the good work. Time to sleep.

You bet! And btw, is that the best you can do?:mrgreen:

I generally agree, although I think the level of contingency in the evolution of life tends to call into question the rationality of the "rational agent".

I don't know what you mean by this statement, since I assume you also believe that there is, in principle, a scientific explanation for everything that happened in the evolution of life. Scientific explanations exhibit rationality in the quite profound sense of conforming to mathematics.

I'd like to know on what basis you think evolution "calls into question the rationality of the 'rational agent'." But first, I would like you to consider the following passages as I think they bear a significant relation to the issues of contingency and rationality we are discussing. I've highlighted a few points which I deem particularly important:

Specifically, the background laws must be such as to allow the conversion of the mass-energy into material forms that allow for the sort of stable complexity needed for life. For example, without the principle of quantization, all electrons would be sucked into the atomic nuclei and hence atoms would be impossible; without the Pauli-exclusion principle, electrons would occupy the lowest atomic orbit and hence complex and varied atoms would be impossible; without a universally attractive force between all masses, such as gravity, matter would not be able to form sufficiently large material bodies (such as planets) for complex, highly intelligent life to develop or for long-lived stable energy sources such as stars to exist. (5)

In sum, even if an inflationary multiverse generator exists, it along with the background laws and principles have just the right combination of laws and fields for the production of life-permitting universes: if one of the components were missing or different, such as Einstein's equation or the Pauli-exclusion principle, it is unlikely that any life-permitting universes could be produced.…..

….All we can say is that if certain seemingly highly specific sorts of laws were not in place, no life sustaining universes could be generated.

link

The laws of nature seem to manifest just this sort of simplicity with variety: we inhabit a world that could be characterized as a world of fundamental simplicity that gives rise to the enormous complexity needed for intelligent life. To see this more clearly, we will need to briefly explicate the character of physical law, as discovered by modern physics. I will do this in terms of various levels.

The physical world can be thought of as ordered into the following, somewhat overlapping, levels First, there are the observable phenomena. This is level 1. The observable world seems to be a mixture of order and chaos: There is order, such as the seasons or the order of day following night, but also many unique, unrepeatable events that do not appear to fall into any pattern. Level 2 consists of a set of postulated underlying entities and processes hypothesized to obey some fundamental physical laws. Such laws might be further explained by deeper processes and laws, but these will also be considered to inhabit level 2. So, for instance, Newton's law of gravity and Einstein's equation of General Relativity would be considered at Level 2. One of the great achievements of science has been the discovery that a deeper order to these phenomena could be found in mathematics. As has been often pointed out, the pioneers of this achievement, such as Galileo, Kepler, Newton, and Einstein, had a tremendous faith in the existence of a mathematical design to nature, though as is well known, Einstein did not think of this in theistic terms. As Morris Kline, one of the most prominent historians of mathematics, points out, "From the time of the Pythagoreans, practically all asserted that nature was designed mathematically …. During the time that this doctrine held sway, which was until the latter part of the nineteenth century, the search for mathematical design was identified with the search for truth. " (1972, p. 153.)

Level 3 consists of fundamental principles of physics. Examples of such principles are the principle of conservation of energy and the gauge principle (that is, the principle of local phase invariance), the principle of least action, the anti-commutation rules for fermions, and the correspondence principle of quantum mechanics. These are regulative principles that, when combined other principles such as that of choosing the simplest Lagrangian, are assumed to place tight constraints on form that the laws of nature can take in the relevant domain. Thus, they often serve as guides to constructing the dynamical equations in a certain domain. Finally, at level 4 is the basic mathematical structure of current physics, for example, the mathematical framework of quantum mechanics, though there is no clear separation between much of level 4 and level 3. Finally, one might even want to invoke a level 5, which consist of the highest-level guiding metaphysical principles of modern physics - principles such as that we should prefer simple laws over complex laws, or that we should seek mathematical explanations for phenomena.

Now, this simplicity with variety is illustrated at all levels, except perhaps level 5. For example, although the observable phenomena have an incredible variety and much seeming chaos, they can be organized via a relatively few simple laws governing postulated unobservable processes and entities. What is more amazing, however, is that these simple laws can in turn be organized under a few higher-level principles (level 3) and form part of a simple and elegant mathematical framework (level 4).

One way of thinking about the way in which the laws fall under these higher-level principles is as a sort of fine-tuning. If one imagines a space of all possible laws, the set of laws and physical phenomena we have are just those that meet the higher-level principles. Of course, in analogy to the case of the fine-tuning of the parameters of physics, there are bound to be other sets of laws that meet some other relatively simple set of higher-level principles. But this does not take away from the fine-tuning of the laws, or the case for design, any more than the fact that there are many possible elegant architectural plans for constructing a house takes away from the design of a particular house. What is important is that the vast majority of variations of these laws end up causing a violation of one of these higher-level principles, as Einstein noted about general relativity. Further, for those who are aware of the relevant physics, it is easy to see that in the vast majority of such cases, such variations do not result in new, equally simple higher-level principles being satisfied. It follows, therefore, that these variations almost universally lead to a less elegant and simple set of higher-level physical principles being met. Thus, in terms of the simplicity and elegance of the higher-level principles that are satisfied, the laws of nature we have appear to be a tiny island surrounded by a vast sea of possible law structures that would produce a far less elegant and simple physics.

As testimony to the above point, consider what Steven Weinberg and other physicists have called the "inevitability" of the laws of nature. (For example, see Weinberg, 1992, pp. 135-153, 235-237). The inevitability that Weinberg refers to is not the inevitability of logical necessity (1992, p. 235), but rather that the mathematical structure of the laws of nature are encompassed by a few general principles. The reason Weinberg refers to this as the "inevitability" of the laws of nature is that the requirement that these principles be met often severely restricts the possible mathematical forms the laws of nature can take, thus rendering them in some sense "inevitable." If we varied the laws by a little bit, these higher-level principles would be violated.

This inevitability of the laws is particularly evident in Einstein's general theory of relativity. As Weinberg notes, "once you know the general physical principles adopted by Einstein, you understand that there is no other significantly different theory of gravitation to which Einstein could have been led." (1992, p. 135) As Einstein himself said, "To modify it [general relativity] without destroying the whole structure seems to be impossible." (Quoted in Weinberg, 1992, p. 135.)

This inevitability, nor near-inevitability, is also illustrated by the gauge principle, the requirement that the dynamical equations expressing the fundamental interactions of nature - gravity, the strong, weak, and electromagnetic forces - be invariant under the appropriate local phase transformation. When combined with the heuristic of choosing the simplest interaction Lagrangian that meets the gauge principle and certain other background constraints, this has served as a powerful guide in constructing the equations governing the forces of nature. Yet, as Ian Atchison and Anthony Hey point out in their text Gauge Theories in Particle Physics, there is no compelling logical reason why this principle must hold (1989, pp. 59- 60). Rather, they claim, this principle has been almost universally adopted as a fundamental principle in elementary particle physicists because it is "so simple, beautiful and powerful (and apparently successful)" (1989, p. 60). Further, as Alan Guth points out, the original "construction of these [gauge] theories was motivated mainly by their mathematical elegance" (1997, p. 124). Thus, the gauge principle provides a good example of a contingent principle of great simplicity and elegance that encompasses a wide range of phenomena, namely the interactions between all the particles in the universe.

Link.

That all seems very rational to me. I'm wondering why it doesn't seem very rational to you.

The relatively quick decline of primary production collapsed those elaborate food webs, resulting in the dramatic increase in extinctions.

It would appear we are now experiencing another food web collapse.

Two good papers discuss this:

Spicer R (1989). Plants at the Cretaceous-Tertiary boundary. Phil. Trans. R. Soc. Lond. B 325 : 291-305

Briggs J (1991). A Cretaceous-Tertiary mass extinction? Bioscience 41(9): 619-624

My point being that just because some event is contingent no more favors the hypothesis that it occured by chance than the hypothesis that it occurred by the free will of a rational agent.

I generally agree, although I think the level of contingency in the evolution of life tends to call into question the rationality of the "rational agent".

At what point should they have evolved opposable thumbs so they could actually do fine manipulation enough to invent real tools?

After 1.78 million years. I'll buy you a drink if I'm wrong.

Give em a few more million years.

At what point should they have evolved opposable thumbs so they could actually do fine manipulation enough to invent real tools?

At any rate, I never bought the idea that dinosaurs had to die off before mammals could come along. The small mammals that existed alongside dinosaurs were not competing for the same resources or filling the same niches. And they did manage to survive the K-T event.

But they could only fill the niches previously occupied by the sauropods because the latter disappeared, or at least their disappearance sped up that process. I don't see a compelling reason why raptors couldn't have evolved tool use and wouldn't have become as clever as chimps or us. But I'm not saying it's likely that that they would have either. Who knows? Some birds like New Caledonian jackdaws or crows are very clever at tool construction and use. Give em a few more million years.

I think it's fair to say that life today is maybe not as contingent on the effects of the KT extinction as we once thought, but that says nothing about the millions of other contingencies (some random, some not) that led us to this point.

Actually, I think it's clear that mammals were/are so much smarter than dinosaurs that they'd have inherited the earth anyway. Especially since the raptors (smartest of the genre) were busy evolving into birds. From the hundreds of dinosaur species we know about, it doesn't look like any of them would have been a match for tool-using, pack-hunting primates.

At any rate, I never bought the idea that dinosaurs had to die off before mammals could come along. The small mammals that existed alongside dinosaurs were not competing for the same resources or filling the same niches. And they did manage to survive the K-T event.