Privileged Planet: Amazon Review

The following review of Privileged Planet was also submitted to Amazon

Gonzalez et al appeal to Dembski’s Design Inference to show how the correlation of habitability and measurability shows evidence of ‘purpose’ in the universe. Various people such as Wein, or various authors on, have already shown what is wrong with the Design Inference argument. I will limit my comments to the claims by Gonzalez et al to show that their appeal to the Design Inference is inappropriate. In addition I will show that their use of correlation to support ‘purpoe’ suffers from poorly defined and thus poorly quantifiable terms, that it is based on a single observation of what they call a ‘constrained optimum’ (the earth), that it is biased towards earth-like planets, and that it is based on cherry picking of examples that support the thesis. In other words, from a scientific perspective their claims are meaningless. Which of course does not mean that their book does not make for a useful apologetic tool (hence my two stars). For people who need their faith to be supported by some impressive sounding but scientifically poorly supported claims, this book serves its purpose. If one is hoping that this book will present a scientific argument for Intelligent Design then one will be quite disappointed.

In simple terms, which would not do full justice to their arguments (hence the length of my review), the main problem of their claims is that on any planet on which life were to develop, complex life would develop some form of ‘science’ and they would believe that their planet is best suited for their science to have developed, ignorant of what they don’t know. For all we know, our science may be light-years behind what science would be elsewhere but how would we know? The authors present no evidence that the expected correlation between our level of science (measurability) and habitability is anything beyond what is to be expected. In other words, we only know scientifically that which we can measure and have no way to know how ‘optimal’ our knowledge is since we have no comparissons.

A quick overview of the Design Inference is in order to understand the shortcomings in the arguments by Gonzalez and Richards. Basically, the ‘Design Inference’ attempts to identify events with low probability (or in the somewhat confusing language of Dembski, high complexity) and a specification (an independently given pattern). Such events are claimed to be ‘designed’. Low probability is determined through elimination of regularity and chance processes, specification is provided through an independent description of the event. It is important to realize that the Design Inference is a purely eliminative argument with all the problems of such an approach such as gap arguments and argument from ignorance.

In addition to others such as Ratzsch and Wimsatt’s critical remarks about the ‘Design Inference’, Richards himself seems to consider the ‘Design Inference’ of limited usability: “We think there are lots of events and structures for which we are rational in concluding “intelligent design,” but for which it is impossible (or really hard) to run a probability on them. If we had to do so to infer design, we would almost always be unjustified in inferring design. For instance, I still don’t know how to run a probability on Stonehenge or the black monolith in 2001: A Space Odyssey. Still, I think both are designed, and I think we’re rational in so concluding.” So in order to be able to be able to appeal to the “Design Inference”, Gonzalez et al have to show that the events are of low probability and that there is an independent specification. My claim is that they have failed in all aspects to make a convincing case. In fact, I intend to show that the authors are aware of the limitations of their use of Dembski’s ‘Design Inference’ yet are still appealing to it to draw their conclusions of ‘purpose’.


“Mankind is unusually well positioned to decipher the cosmos.” From: Gonzalez and Richards, The Privileged Planet: How our place in the cosmos is designed for discover.

But Gonzalez et al provide no quantifiable measures that help us determine if their claim is correct. What they do argue, again without much supporting evidence, is that habitability and measurability correlate in zones that are called galactic ‘habitable zones”. They argue that these zones are ‘rare’ but present no quantifiable information as to how many stars would be involved. The statement that habitability and measurability correlate in (significantly sized) zones in the universe undermines the argument that habitability and measurability are improbable and even seems to argue that measurability and habitability naturally correlate.

Even more mysterious than the fact that our location is so congenial to diverse measurement (what is so mysterious about this? Other than that the authors have failed to make their case that the earth is uniquely congenial to diverse measurements) and discovery is that these same conditions appear to correlate with habitability (appear to correlate. That’s the risk of not really providing for hard estimates). This is strange because there is no obvious (to the authors at least) reason to assume that the very rare (unsupported) properties that allow for our existence (anthropocentric) would also provide the best overall (and yet the authors provide NO evidence for this optimality) setting to make discoveries about the world around us.

So lets look at some of the examples of measurability they quote from a variety of disciplines. Their article include perfect solar eclipses (astronomy), ice cores in Greenland and Antarctica (geology), deep sea cores (geology), tree rings (biology), stellar trigonometric parallax (astronomy). Stars as isotropic emitters of highly specific information (any ID paper seems to have as a requirement a reference to information and specificity J), supernovae and Cepheids (astronomy), our place in the Milky way and dust extinction (astronomy), the capacity to observe the maximum diversity of star types and the distant universe (astronomy) background radiation (astronomy) and the particle and event horizons of the universe (astronomy). Not as diverse as one may have hoped for and in fact the authors fail to show that the earth is somehow unique in these aspects

So is the earth ‘the best overall bench in the lab’? The authors do little to support this conclusion other than by pointing out that the earth has certain characteristics but are they optimal? Are they the best bench in the universe? How will we know? Little guidance is provided here.


Gonzalez suggests that there is a link between life (on earth) and perfect solar eclipses. The moon and sun appear to be of similar size in the sky allowing ‘perfect’ solar eclipses to occur. Not only is a big moon essential for stabilizing the planet (helpful perhaps but not necessarily essential)but it also was essential for the validation of Einstein’s theory of relativity and the study of the solar corona. Thus linking habitability with measurability. But was the solar eclipse of 1919 required for the scientific discover of Einstein? It’s hard to argue that this confirmation hurt Einstein’s case but lest point out that first of all, Einstein did not base his theory on the solar eclipse so the origins of the theory are not dependent on the solar eclipse but what about its verification? To understand the relevance of the 1919 solar eclipse we need to remember that Einstein provided in his 1915 paper three experimental tests.

Would the precession of the perihelion of Mercury not have been sufficient? Would the solar eclipse data have been sufficient without the Mercury prediction? In fact to Einstein “This discovery was, I believe, by far the strongest emotional experience in Einstein’s scientific life, perhaps in all his life. Nature had spoken to him.” Abraham Pais (EM, p. 202)” “.

Einstein commented: “These equations, which proceed, by the method of pure mathematics, from the requirement of the general theory of relativity, give us, in combination with the [geodesic] equations of motion, to a first approximation Newton’s law of attraction, and to a second approximation the explanation of the motion of the perihelion of the planet Mercury discovered by Leverrier. These facts must, in my opinion, be taken as a convincing proof of the correctness of the theory.” The same source reports that: To his friend Paul Ehrenfest in January 1916 he wrote that “for a few days I was beside myself with joyous excitement”, and to Fokker he said that seeing the anomaly in Mercury’s orbit emerge naturally from his purely geometrical field equations “had given him palpitations of the heart”.

But of course Mercury and habitability arguments just do not seem to be as impressive as trying to present a case that the moon provides for stability of the earth axis (habitability) and allows for discovery (measurability). Certainly the perihelion of Mercury was an earlier event than the 1919 solar eclipse. We may never know to what extent the solar eclipse data sealed the case for Einstein’s theory but it does show how the data appear to be carefully selected to support the thesis.

Here we also encounter another peculiarity of Earth namely that the requirement for habitability (nearly circular orbit) made the earth orbit unreliable for perihelion precession measurements.


Gonzalez et al attempt to make their case for the design inference by first pointing out that: “ Complexity is improbability” (finally a clear definition of Dembski’s version of complexity) and argue that:

  1. Conditions that allow for habitability are improbable
  2. The conditions that allow for measurability are improbable.

Let’s look at there terms in more detail:


But is this correct? Are conditions that allow for habitability improbable? Dembski requires a probability of 10^-150 before a design inference can be triggered. In addition Dembski requires the elimination of chance and regularity pathways while Gonzalez et al only consider chance pathways. Richards argues that “But what if you want to know if, say, the structure of the natural laws themselves, or the cosmos as a whole, is the result of purpose or design? Well, you’ll at least need to modify Dembski’s approach.” In other words, when Gonzalez et al infer ‘purpose’ they include natural law as the ‘designer’.

Richards seems to recognize the challenges and limitations of the ‘Design Inference’ approach when stating on ISCID that: “We view Dembski’s arguments as a valuable rational reconstruction for capturing an important subset of designed structures. We also think he makes a critical insight that design detection has as much to do with pattern recognition as with probabilities. However, Dembski’s reconstruction is optimized to avoid false positives, not to allow a design inference for all discernibly designed structures. So it shouldn’t be treated as a Procrustean Bed into which we have to fit everything that’s discernibly designed.” In that light Richards states that “Also, while we use Dembski’s criteria for detecting design, we don’t depend on them exclusively. We also draw on the work of John Leslie, Del Ratzsch and others.”. My biggest gripe with this is that despite this, Dembski’s ‘Design Inference’ is given a central position in arguing for ‘purpose’ in public presentations and even in the book itself.

Do we know enough about the parameters for habitability to be able to state that conditions for habitability are improbable? I claim that at most one can argue that with our present knowledge we simply do not know. Certainly it is far too early to argue that habitability is improbable.

In addition, habitability is defined in terms that treat our own situation preferentially. In other words habitability describes a ‘terrestrial’ planet not too warm, not too cold with water and oxygen. Add some ad hoc requirements, like those used by Gonzalez et al, such as for example a large moon, plate tectonics, a large planet to deflect some of the incoming threats etc and one can make a case for the uniqueness of earth. But a similar argument could be made for almost anything. By tightening the requirements for habitability to describe the present situation for our earth one can indeed reach a small probability but then the question becomes one of prediction. Is the earth unique or have we forced upon it enough criteria that make it appear to be unique? Has habitability become a description rather than a prediction? Or in other words are the requirements set for habitability that lead to a low probability actual requirements or ‘ad hoc’ descriptors of our own situation. In other words are we making our own earth ‘privileged’? If that is the case the outcome is not surprising. However any claim of ‘purpose’ seems to be leaping to conclusions.

While one can certainly attempt to tighten the probabilities, one should not ignore those circumstance which would loosen the probabilities such as the fact that we can only observe a fraction of the total Universe or that habitability requirements need to be loosened to take into consideration other forms of life.

And finally, habitability is not a concept easily quantified. Arguments of improbability thus become subjective claims.


Definition: Measurability refers to those features of the universe as a whole, and especially to our particular position in it - both in space and time - which allow us to detect, observe, discover and determine such features as the size, age, history, laws and other properties of the physical universe. Gonzalez et al claim that they do not argue is that every single condition for measurability is optimized on the Earth’s surface or that it is easy to make measurements and scientific discoveries on Earth. The argument is that the Earth allows for a “stunning diversity of measurements, from cosmology and galactic astronomy to stellar astrophysics and geophysics; and it allows for this rich diversity of measurement much more so than if Earth were ideally suited for, say, just one of these sort of measurements.” So in other words, the earth is ‘optimal’ in a weighted, statistical sense. But is that really supportable with quantifiable evidence? I argue that the authors have failed to show that this is the case. Largely because the concepts of habitability and measurability have not been given quantifiable values. The authors argue that they have avoided ‘cherry picking’ by taking examples from every important discipline. As I will argue, they have done so at the cost of ignoring examples that show poor measurability and thus have failed to show that the earth is somehow unique in this aspect.

So what about measurability? As with habitability, measurability lacks a workable definition, but it also suffers from a selection bias. In case of habitability we may make the mistake of using factors typical for our earth as relevant to habitability in general. With measurability, the same problem arises in that what we cannot measure will remain unknown. So what is the full space of measurability versus what we can actually measure on earth? How do we know if we are optimal if we cannot define measurability due to our ignorance?

In other words, either measurability is trivially true (we measure what we can measure) or it is fraught with an appeal to ignorance since we fail to consider that which we do not know.

Gonzalez et al argue that the moon is an important factor for measurability since ‘perfect solar eclipses’ allowed verification of Einstein’s theory of relativity and the study of the corona. As Gonzalez et al point out, these eclipses are not really perfect due to the eccentricity of the Earth and Moon’s orbits.

How do we know that Einstein’s theory would have fared worse or better if the earth had not had perfect eclipses? If the earth is such a special place how come that astronomy had to wait for space based platforms before it really took off? I will look in more detail into some of the examples used by Gonzalez and show that they do not support their claims.

In summary I argue that the authors have failed to show that measurability and/or habitability are improbable. In fact I argue that given the present status of our scientific investigations and knowledge, any such claim of improbability runs the risk of ‘appeal to ignorance’.


In addition to improbability, the Design Inference also a requires a specification. Remember that one of the requirements for this specification is that it is independent of the event. According to Gonzalez “The correlation of habitability and measurability forms a meaningful pattern” or in other words, a specification. Are they correct? Once again I have to disagree with their claim for a variety of reasons. First of all they have not shown that the correlation between the two is independent. In fact the existence of a correlation suggests that these two events are NOT independent. What if measurability is strongly correlated with habitability through some form of necessity? In fact, Gonzalez argues that the correlation between the habitability and measurability effects of the Moon can be explained by natural law. Surely appealing to natural law as the designer of ‘purpose’ seems to weaken their argument.

In addition the authors base their claims on a sample size of one. While the authors try to defuse this criticism by arguing that they have in fact many examples from a variety of disciplines their correlation argument is based on a single data point namely ‘earth’. No other examples of ‘habitable’ environment are described. Under such circumstance, one should frown upon any claim of correlation. Especially when measurability and habitability are poorly defined, and unquantified.


Let me give you an interesting example that I hope will clarify some of my objections. When studying data on ice-cream sales and the number of drownings, it was found that there existed a strong correlation between the two. Using the same Design Inference approach chosen by Gonzalez et al, one may argue that drownings are improbable and in addition that the correlation between drownings and ice-cream sales shows evidence of a specification. In other words one should conclude, according to these authors, “design” or purpose. While I am not sure why one would expect design in something like drownings, this example shows the risks involved in using the approach chosen. And in this example ice-cream sales and drownings were actually quantifiable; not much ignorance on our part as to their exact numbers. So statistically the case is much stronger than the case made by Gonzalez et al.

Of course we all ‘know’ that the correlation was not evidence of ‘design’ but caused by a third independent factor namely ‘sun shine’. Since more people go out swimming during sunny days and since more people eat ice-cream during sunny days one quickly realizes that this correlation was due to a third factor. So what if measurability and habitability are intrinsically correlated or correlated through a third factor? I could think of various reasons why this may be the case.

As an interesting side-note, in addition to drownings, correlations have been found between ice cream sales and murder, boating accidents, and shark attacks.


My biggest gripe is with the authors’ confusion of design and purpose. While science can show function, showing purpose requires a philosophical or theological assumption or direct or indirect knowledge of the motivations of the designer. While Dembski denies that motives, opportunity, means etc are indispensable for a reliable design inference, actual design inferences in archeology, criminology and SETI strongly depend on such assumptions. Would a designer be interested in correlating habitability and measurability and that uniquely to earth? Perhaps, but such an argument is easier made based on theological assumptions than based on unbiased assumptions. Without much knowledge about motives, stating that the correlation between the habitability and measurability is what we would from a designer seems somewhat circular.

In other words. when purpose is inferred based on our ignorance then we enter a dangerous realm of ‘gap arguments’. Gonzalez et al argue that a designer would be interested in having his creation learn about the world and universe they live in hence measurability and habitability would be expected to correlate. But then again, there may be regularity and chance processes that result in a similar correlation. Lacking a clear definition of both habitability and measurability and the inherent observer bias, it is hard to argue that we can reach a design and purpose inference. After all how can we eliminate regula


My claim is that it is exactly in areas where life and science develop were expect to see science discover a correlation between habitability and measurability. Without habitability we would not have been here, without measurability we would not have science to lead us to this conclusion. Does this mean that there was purpose involved, or just a matter of fact statement?

Isn’t a beach well adapted for sun bathing, digging holes in the sand, beach volley ball and wading. Isn’t it miraculous that we go to beaches, which provide for easy access to the ocean, with sand allowing us to spend our sun bathing in relative comfort and play beach games. In addition a slowly deepening bottom allows us to wade in the ocean without the immediate risk of drowning. As icing on the cake, the waves seem to approach the beach in perpendicular to the coast line adding to our enjoyment. And in addition to all this, what surely must seem to be a miraculous environment, also provide us with protection from flooding (dunes). One cannot escape the conclusion that these beaches were designed with a purpose in mind. (I would like to thank my unnamed colleague who came up with these excellent observations).


Assume that a habitable environment exists with an opaque atmosphere, or at least opaque to ‘visible’ light (visible to us that is). Would it not be reasonable to expect that the local life forms might evolve a ‘vision’ in a range in which the atmosphere is not opaque? What exciting discoveries could such an organism make in these wavelengths? And how would they lament these poor creatures on planets with opaque atmospheres. So is measurability not in the eyes of the beholder?

A review of critiques

In 2002, a five-part debate on the hypothesis of ‘Rare Earth’ took place on website. One of the participants, David Grinspoon remarked

David Grinspoon: I think it is a mistake to look at the many specific peculiarities of Earth’s biosphere, and how unlikely such a combination of characteristics seems, and to then conclude that complex life is rare. This argument can only be used to justify the conclusion that planets exactly like Earth, with life exactly like Earth-life, are rare.

My cat “Wookie” survived life as a near-starving alley cat and wound up as a beloved house cat through an unlikely series of biographical accidents, which I won’t take up space describing but, trust me, given all of the incredible things that had to happen in just the right way, it is much more likely that there would be no Wookie than Wookie. From this I do not conclude that there are no other cats (The Rare Cat Hypothesis), only that there are no other cats exactly like Wookie.

Life has evolved together with the Earth. Life is opportunistic. The biosphere has taken advantage of the myriad strange idiosyncrasies that our planet has to offer. Not only that, life has created many of Earth’s weird qualities.

So it is easy to look at our biosphere, and the way it so cleverly exploits Earth’s peculiar features, and conclude that this is the best of all possible worlds; that only on such a world could complex life evolve. My bet is that many other worlds, with their own peculiar characteristics and histories, co-evolve their own biospheres. The complex creatures on those worlds, upon first developing intelligence and science, would observe how incredibly well adapted life is to the many unique features of their home world. They might naively assume that these qualities, very different from Earth’s, are the only ones that can breed complexity.

Darling published a detailed criticism of the ‘Rare Earth’ hypothesis in his book “Life Everywhere: The Maverick Science of Astrobiology.” Much of his comments apply to the Privileged Planet claims as well. But there are some differences between the arguments in Privileged Planet and Rare Earth, which I will discuss.

Darling quotes Athena Andreadis, a neuro surgeon at Harvard Medical School who points out that: “In science, theories cannot be identical to their predictions, nor can that prediction be trivial. In fact, the Rare Earth theory is neither hypothesis nor prediction, but a description of how life arose on earth… Their (Ward and Brownlee’s) oft repeated statement that both Earth and humans are unique is neither novel not contested - nor helpful in predicting life elsewhere.” While these objections are about Ward and Brownlee’s book ‘Rare Earth’ they appear to apply equally well to the “Privileged Planet”.

Darling continues to argue that: “But Ward and Brownlee go further, they actually pick and choose the factors that best suit their case.” Again the same criticism applies equally well to the Privileged Planet.

See also “A Critique of the Privileged Planet Hypothesis” by Kyler Kuehn presented at the “The Heavens Declare the Glory of God” ASA Annual Meeting, July 25-28, 2003 Colorado Christian University

In a recent comment the authors add:

“Of course, as we say several times in the book, we don’t argue that the Earth is optimal for observing every particular type of phenomenon we cite. Rather, it’s optimal in the constrained sense of providing the best overall place for discovery.” Notice the vagueness of the statement. ‘Optimal in the constrained sense’… Notice also the lack of much supporting evidence that this is indeed the case. Other than cherry picking some examples which the authors believe support their argument while ignoring or objecting to examples which any reasonable observer would consider to be detrimental to their arguments using the ‘escape clause’ of vagueness. This further supports my thesis that the authors of PP have not only poorly quantified the terms measurability and habitability but also have failed to show that there is significant correlation or even some optimization (in a constrained) sense. When the earth is a better place for discovery it is hailed as evidenc in support, when the earth is a worse place for discovery it is hailed as evidence for ‘constrained optimization’.

The authors should by now be quite exhausted flapping their arms.

The authors continue: “So, even if it were easier to measure the perihelion advance from Mercury or Venus (neglecting its thick cloudy atmosphere), this would have to be balanced with other important scientific discoveries that depend on distance from the Sun. For instance, Mercury and Venus would offer poorer platforms for measuring stellar parallax because they orbit closer to the Sun.” Again, unquantified arguments to support some form of ‘constrained optimization’ are not very helpful in furthering their claims. Of course we can focus on specific examples supporting their thesis while ignoring the many other examples which disprove their thesis but that would be ‘cherry picking’. In fact, let’s assume that the earth is a horrible place to observe the more interesting aspects of astronomy, how would we know?

The authors end with: “Finally, we don’t argue that Earth is unique. Discovering another planet around another star in the Galaxy would be quite compatible with our hypothesis, so long as that planet is genuinely Earth-like. Finding a fundamentally different planet with (native) complex life on it, in contrast, would contradict our argument that the conditions for life and scientific discovery correlate in the universe.” Why? That statement does not make sense at all. Is the argument suddenly that it is not the correlation of habitability and discovery but rather earth-like life and earth-like discovery. Surely the authors must realize that their claim is self-contradictory. Let’s assume we find a non-earth like planet with complex life which is able to perform scientific discoveries, does this negate the authors’ claim about correlation between life and scientific discovery? Not really. But it does show the underlying problem with the authors’ premise that the earth is special which leads them to make this self contradictory statement.

The authors may wish to argue that earth-like is synonymous with habitable or measurable but such an approach would make their argument seemingly tautological.

Of course if one take the earth as a standard for habitability AND scientific discovery then it is no wonder that one may conflate the two concepts. But it is hardly impressive to hear the authors comment on an observation of 1 to infer a correlation between habitability and discoverability. And before the authors object by saying that they show several such examples, let it be clear that the authors themself are arguing for a ‘constrained optimization’ which means that a single observation cannot be independent of another observation but rather that when taking into consideration all aspects of habitability and discoverability for lets say the planet earth one has one example of a constrained optimization (in a statistical sense). Otherwise any observation which contradicts the authors’ viewpoint would count as an example against their thesis. But they insist that such observations do not affect their arguments. Hence the conclusion is simple, earth can be at most a single datapoint of an ‘constrained optimization’.

Of course this does not even address how the optimization is ‘constrained’ or in what sense one has to determine optimality.

From an apologetic perspective of course it is not surprising that one may reach the premise that the earth is special. But one should also be aware that such premise may lead one to ignore facts contrary to such a premise under the argument of ‘constrained optimization’. Such an argument however merely indicates the weakness of the premise.

Assuming that the earth was indeed created by an omnipotent Creator, why should we expect that such a Creator would place the earth in a position of ‘constrained optimum’? Do we really want to assume that the Creator was constrained in what could be achieved?

Scientifically and theologically I believe such a position becomes quickly untenable.

I will address in a followup posting their comments on the relevance of the perihelion to the theory of relativity. This posting intends to address their self contradicting statement which reveals the underlying premise of their argument .