The Probability of God: A Simple Calculation That Proves the Ultimate Truth

by Stephen D. Unwin

Does God exist?

This is probably the most debated question in the history of mankind. Scholars, scientists, and philosophers have spent their lifetimes trying to prove or disprove the existence of God, only to have their theories crucified by other scholars, scientists, and philosophers. Where the debate breaks down is in the ambiguities and colloquialisms of language. But, by using a universal, unambiguous language—namely, mathematics—can this question finally be answered definitively? That’s what Dr. Stephen Unwin attempts to do in this riveting, accessible, and witty book, The Probability of God .

At its core, this groundbreaking book reveals how a math equation developed more than 200 years ago by noted European philosopher Thomas Bayes can be used to calculate the probability that God exists. The equation itself is much more complicated than a simple coin toss (heads, He’s up there running the show; tails, He’s not). Yet Dr. Unwin writes with a clarity that makes his mathematical proof easy for even the nonmathematician to understand and a verve that makes his book a delight to read. Leading you carefully through each step in his argument, he demonstrates in the end that God does indeed exist.

Whether you’re a devout believer and agree with Dr. Unwin’s proof or are unsure about all things divine, you will find this provocative book enlightening and engaging.

“One of the most innovative works [in the science and religion movement] is The Probability of God ...An entertaining exercise in thinking.”—Michael Shermer, Scientific American

“Unwin’s book [is] peppered with wry, self-deprecating humor that makes the scientific discussions more accessible...Spiritually inspiring.”-- Chicago Sun Times

“A pleasantly breezy account of some complicated matters well worth learning about.”-- Philadelphia Inquirer

“One of the best things about the book is its humor.”-- Cleveland Plain Dealer

“In a book that is surprisingly lighthearted and funny, Unwin manages to pack in a lot of facts about science and philosophy.”-- Salt Lake Tribune

Genres: Religion, Mathematics, Spirituality, Philosophy, Nonfiction

259 pages, Paperback

First published October 25, 2000

About the author

STEPHEN D. UNWIN was born in Manchester, U.K. He attended Chetham's Hospital School and obtained his bachelor's degree in physics from Imperial College, University of London. For his research in the field of quantum gravity, he received his doctorate in theoretical physics from the University of Manchester. He has held the post of British technical attaché to the United States Department of Energy, and founded Unwin Company, a consulting firm specializing in risk analysis and risk management for Fortune 100 clients.

Reviews

[Manuel Alfonseca · Rating 3 out of 5]

ENGLISH: This is a strange book, which claims to compute the probability that God exists by applying the Bayesian theory of probabilities. Of course, the result (67%) depends on many assumptions the author has made, and he is conscious of the fact, and proposes that the readers make their own computations.

Chapter 3 is the major failure in the book. Unwin uses it to discredit all arguments based on physics and biology (i.e. arguments based on fine tuning). Unwin's reasoning can be summarized like this: Being amazed because the universe seems adjusted to make life possible is equivalent to being amazed because, when you are in front of the map of a shopping center and look at an arrow marked "you are here," in fact, you are here.

But this reasoning is wrong. If you are in front of the map and see that everything matches, what is amazing is that the map is true to the structure of the shopping center, and that it is placed precisely in the right place so that the "You are here" arrow is correct. This is an obvious sign of design: someone has designed the map to be true to the shopping center, and someone has placed it in the correct place for the arrow to be right. Therefore, the existence of the map with its arrow is an important argument in favor of design. Obviously, not only Unwin has not understood the fine-tuning argument, but he has not even understood his own parallel.

However, the discussions in chapters 9 and 10 are excellent. I would keep this quote: There are many bright, accomplished people who are people of faith. I think that it’s in their nature to be analytical and to seek to uncover rational justification for their beliefs. So they apply their intellectual resources to the task and often produce articulate, structured cases for God... They entered their analysis with faith in the existence of God. The conclusions of their analysis were thus hardwired from the outset, and they merely sought an articulate, credible route to the predetermined end point... So the process of justifying faith is in my opinion a very artificial one... AXE: Wouldn’t you accuse atheists of the same thing? They’ll enter into an assessment of the evidence for God having predecided their conclusions. CHAD: I agree. They’re equally disingenuous..

I've frequently asserted that the difference between an atheist and a believer is that the believer starts from the axiom God exists while the atheist starts from the axiom God does not exist. From those starting points, reason starts to act. Therefore, in principle I agree in this point with Chad's analysis, but I wouldn't call atheists and believers disingenuous. Those who do that, being conscious of what they are doing and why they are doing it, are not disingenuous.

ESPAÑOL: Este es un libro extraño, que pretende calcular la probabilidad de que Dios exista aplicando la teoría bayesiana de probabilidades. Por supuesto, el resultado (67%) depende de muchas suposiciones que ha hecho el autor, aunque él es consciente de ello, y propone que los lectores hagan sus propios cálculos.

El capítulo 3 es el mayor fallo del libro. Unwin lo utiliza para desacreditar los argumentos basados en la física y la biología (es decir, los argumentos basados en el ajuste fino). Su razonamiento puede resumirse así: Asombrarse porque el universo parece ajustado para que sea posible la vida equivale a asombrarse porque, cuando estás delante del plano de un centro comercial donde pone "usted está aquí", efectivamente, usted está aquí.

Pero este razonamiento es erróneo. Si estás delante de ese plano y todo coincide, lo que es asombroso es que el plano sea fiel a la estructura del centro comercial, y que esté colocado precisamente en el sitio adecuado para que la flecha "Usted está aquí" sea correcta. Esto es un indicio evidente de diseño: alguien ha diseñado el plano para que sea fiel al centro comercial, y alguien lo ha colocado en el sitio correcto para la flecha. Por lo tanto, la existencia del plano con su flecha es un argumento importante en favor del diseño. No sólo Unwin no ha entendido el argumento basado en el ajuste fino, sino que ni siquiera ha entendido su propio paralelo.

Sin embargo, la discusión de los capítulos 9 y 10 es excelente. Me quedo con esta cita: Hay muchas personas brillantes que son personas de fe. Creo que está en su naturaleza ser analíticos y tratar de descubrir una justificación racional para sus creencias. De modo que aplican sus recursos intelectuales a la tarea y a menudo producen casos articulados y estructurados [en favor de la existencia de] Dios... Empezaron su análisis con fe en la existencia de Dios. Por lo tanto, las conclusiones de su análisis estaban programadas desde el principio, y ellos simplemente buscaban una ruta creíble hacia el punto final predeterminado... Así que, en mi opinión, el proceso de justificar la fe es muy artificial... AXE: ¿No acusarías a los ateos de lo mismo? Antes de buscar evidencia sobre la existencia de Dios ya habían sacado sus conclusiones. CHAD: Estoy de acuerdo. Son igualmente insinceros.

He afirmado muchas veces que la diferencia entre un ateo y un creyente es que el creyente parte del axioma Dios existe mientras que el ateo parte del axioma Dios no existe. A partir de estos puntos de partida, la razón comienza a actuar. Por lo tanto, en principio estoy de acuerdo con el análisis de Chad en este punto, pero yo no llamaría insinceros a los ateos y creyentes. Quienes hacen esto, siendo conscientes de lo que hacen y por qué lo hacen, no son insinceros.

[Andrew Breslin · Rating 3 out of 5]

All the philosophers and theologians are going to have find something else to debate, because the question of whether or not "God" exists has finally been answered. With math! Glorious math! Is there nothing it can't do? First it helped us find the length of the hypoteneuse, and now this! Good luck finding another job, folks. What's that? You're thinking of going into print journalism. Wow, I'm afraid I have some more bad news . . .

Actually, I'm just teasing. Your jobs are at least as secure as anyone else's, and probably much more so than anyone who works for a newspaper. In spite of the subtitle, this thoughtful book makes no such grandiose claims to present "a simple calculation that proves the ultimate truth." I'm quite certain the publishers tacked that on to sell more books. Claiming to provide the ultimate answers to grand celestial questions is a great marketing ploy to sell lots of books to a gullible audience. Witness the phenomenal sales of the Bible and Koran, neither of which, incidentally, are nearly as genuinely thought-provoking as this, but which have much better PR machines behind them.

This book did not provoke the slightest change in my own philosophical perspective concerning the existence of a hypothetical omnipotent entity out there. Far more interesting to me was the discussion of Bayesian analysis, and an introduction to the idea that probability can be a far more complex idea than we assume it to be.

Ultimately, I think that Dr. Unwin earnestly wants to believe in the existence of God, but his rigorous scientific thinking does not allow him to do so without framing what he wants to believe in a context of mathematical formalism. The majority of people in the world are theists and would, if asked, ascribe a 100% probability to the existence of God. A small minority are atheists and would ascribe a 0% probability, or would instead ascribe a 100% probability to the existence of a flying spaghetti monster, but only to piss off the theists. They don't really believe that they have been touched by His noodly appendage.

Another minority would describe themselves as agnostics, implying a probability of God by their calculations somewhere between 0% and 100%. But very few of them could be more specific than that. Personally, I find the entire question of "whether or not God exists" to be silly and meaningless, but I have to give Unwin some credit for at least trying to apply some mathematics to his faith and his doubt, quantifying it, so that theology, digital for dozens of centuries, has finally gone analog.

He concludes with a 95% probability of the existence of God, applying Bayesian analysis to his own admittedly subjective beliefs. I don't agree with him, and the beautiful thing is that I'm sure he'd be 100% okay with that. I neither believe nor disbelieve in the flying spaghetti monster either, but I am 100% confident that it is at least as probable that it exists as any other hypothetical deity. May marinara be upon Him.

[James · Rating 5 out of 5]

Using Bayesian probability, physicist Stephan Unwin attempts to show "The Probability of God". He does a far better job of explaining Bayesian probability than all the Christian apologists I have ever seen, so most people won't have a problem understanding the calculations in rest of the book. (and understanding them correctly)

Unwin starts off with an unsubstantiated a priori probability that God exists of 0.5, then at the end triumphantly declares the probability God exists lies around 0.6. Therefore, it is more probable than not. The first problem lies in his a priori probability of 0.5, in that he claims it is just as likely that God exists as not. He doesn't provide anything of substance to support his claim other than more or less a feeling that it should be equally for and against. To me, this is just as intuitive as saying the proof of God is self-evident by simply looking at the world around us. While Unwin does not make this exact claim, an a priori probability of 0.5 is certainly not supported. (either by Unwin or at all)

One by one, he addresses various aspects of the world and assigns a probality for the existance of God based on these aspects. Combined with the previously calculated probability he arrives at a new probability before moving on to the next topic. In the end, he reaches a probability high enough to maintain that it is probable God exists. Like the a priori probability, the values Unwin choose are arbitrary. Admittedly, most are supported, but the supporting evidence also makes a number of assumptions that one should not blindly accept. It is clear that Unwin is a believer and is "stacking the deck" in favor of a higher probability. (consciously or not)

The reason I am giving this 5 stars is that despite these (in my opinion) incorrect assumptions, Unwin does a fantastic job of explaining the process of deciding the how much a particular aspect supports the probability of God and explaining how this effects the final probability. I most certainly reached a far different conclusion thatn Dr. Unwin, but the methodology he used is completely sound. Despite the apparently bias towards a high probability, it is definitely not as blatant as others (e.g. Richard Swinburne). In reaching a different destination, it was fascinating to have Dr. Unwin accompany me on the journey.

If this is topic you are interested in, I cannot recommend this book enough. It is well-written and is flavored with a style of humor that I find extremely enjoyable. Douglas Adams would be proud.

[Zac]

first off, i am an atheist. stating that first and foremost attempts to lend more credibility to my statements in that i'm not trying to hide anything. anything i say can be built from that context. the author doesn't come out until well into the book about his beliefs which struck me as deceitful. seeing that he was a physics professor and a risk-analysis consultant, i figured he would know that stating all assumptions upfront is standard practice (e.g. i'm a physicist, risk analyst, and a believer and i intend to...).

for a person versed in the details of risk assessment, the author didn't really strike me as a very thorough or detailed person. his introduction to bayesian probability analysis was fairly concise and informative, but once he gets to actually attempting to quantify the probability that god exists, he starts to falter. for one, he's extremely qualitative about how things like natural disasters could be more prevalent in a society with a god or one without. he uses terms i'd paraphrase as "i think this is very likely" or "this might happen more than it wouldn't". granted, there isn't much data to go by, but there IS still some data to be found in the bible. for example, how many people died directly at the hand of god. this would be a direct factor that bad things can happen FROM god in a god-society. you could also include all the bad things that can happen from people themselves in a god-society (i.e. sodom and gomorrah). these could give a more numerical and (as best as can be derived) factual basis for the probabilities he then ascribes to certain things.

i understand that as an atheist i have my bias as does everyone, but i believe that bias is less contaminating in this case since my bias it towards quantification, the exact thing this book proposes it is trying to do. had he only used the bible as a reference book, i think this could've been a better book, by and large. rather, it turned out to be a book of personal bias and indoctrination cloaked in the guise of science, very reminiscent of intelligent design. the author tries to handicap himself by stating something long the lines of "your probabilities may differ according to your beliefs and life experiences", thus making it sound like you might get different probabilities because you believe different, when you actually would be more likely to get different numbers if you actually tried, even modestly, to quantify anything from the bible and religious action around the world.

[Alex Lee · Rating 3 out of 5]

No doubt, the title is marketing. Because as Stephen D. Unwin, PH.D. should know, a probabilistic analysis is not a proof of anything.

We have here a particularly interesting way to 'calculate' God, which is the presentation of the pure form of Bayesian probability with Unwin presenting all the percentages as a gut feeling of sorts. He admits this is wholly subjective but it is equally subjective as far as how we want to pose the question, what metric we want to use to clarify our parameters and how much we ought to weigh what kind of "signs" we would accept. There is all together too much choice in the matter... but that is the point!

One way to resolve this is to realize; the fact that we have a choice in what matters to us is proof that our metrics are up to us... that since there is no obvious metric to choose from there is equally no obvious view that is the official view of the universe. If there were such a view then there would have to be an official point in the universe, more official than any other. We would then be able to resolve this issue of God easily. Not only that, but all conflicts would be shown to be resolvable. In relationships often we do not realize if we are projecting our issues or if the other party has an unaware intention that we are picking up on. This undecidability is in fact one way to understand that 1. there is no official view and 2. that any view that were official or even incredibly consistent (such as one's own point of view) will have problems resolving certain situations in terms of that consistency. I am referring to Godel's incompleteness theorem.

I imagine that Unwin did not want to tackle such an issue in his book, as it could push the premise of a proof of God beyond the scope of his work... he may alienate truly hopeful God-seekers.

Nonetheless, from a theoretical physicist, I would have hoped at least some level of discussion of this caliber. Perhaps such an idea for Unwin is only expressible in terms of math, and not in terms of logic.

Still, this book is easy to read. It is clear, and provides many interesting points, all of which hang on Unwin's presentation of his proof. This book seems to resolve something for Unwin. It does give many interesting points to grasp though, including about the nature of faith given the supposed fairness of God. Worth taking a look at.

[Don Morrison · Rating 1 out of 5]

A joke of a book. Don't waste your time.

Just awful. Lacks coherence and logic. How could anyone write something so vapid and moronic is the real miracle of life.

[Robert Schneider · Rating 3 out of 5]

When a friend asked me to read and review “The Probability of God,” because he knew my position on the topic (0.000000000001%), I thought I’d try to give the book a fair chance and an objective review. I give it 3 stars because it is clear, well written and semi entertaining.

There is only one redeeming element of content in this book, and that is the chapter on the math of faith. In this chapter Unwin describes how all of our belief decisions are ultimately estimates that a proposition is true. I firmly “believe” that every action we take is based on the combined calculation of experiential evidence, factored against the unknown and the likelihood that our chosen action will achieve our desired result. Pretty fancy way of saying that, no matter how much calculation you put into an action, in the end all of us “wing it” at some point.

But should we spend ANY time building the foundational support for our future leaps of faith on empty propositions like “God Exists?” or should be compiling more and more experiential evidence? I vote the latter.

The project of a fair review begins collapsing in upon itself rather quickly. Within the first few pages, Unwin makes clear that the importance of this book is the application of Bayesian statistical calculations, and not a rehash of theist or atheist positions, and so he declares,
“Summarizing, our objective is to calculate the probability that
God exists.”
The brakes on my train of thought screeched as I hit the emergency stop lever. Probability is a science applied to the likelihood of events happening. I’m not the mathematician Unwin is, so please forgive any minor misphrasing, probability is aptly applied to propositions like, “What is the probability that a coin flipped 100 times will come up heads?” Tangible, measurable, definable entities like “coin” and “flipping” and “100” factor into the ability to state a probability.
“God exists” is a meaningless statement containing nothing tangible, measurable or definable to which probability can be attached. But I probably shouldn’t abandon the book so quickly. 5 pages seems like an inadequate sampling. (It takes up until chapter 11 for Unwin to discuss the meaning of “exists.”)
Sure enough, by Chapter 1 Unwin was addressing my concern. The stated central goal of chapter 1, to establish “What shall we mean by the word God in our central proposition: God exists?” We shall face a conundrum of “common language” fuzziness, Unwin warns. “Flight 360 for Cincinnatti is showing an on-time departure.” Completely meaningless out of context. But is Unwin going to argue that we have as much context for “God” as for “Cincinnatti”?
Let me spare you the machinations of Chapter one to arrive at its conclusion: “We will use the word God in the traditional sense associated with the major monotheistic faiths and not in a more philosophical, abstract way.” Traditional Sense? If that were so clear, perhaps we wouldn’t have 10,000 different sects of Christianity, Judaism and Islam.
Chapter two proceeds to compare a mall “You are Here” map to the universe, with predictably inapt results and conclusions. The mall is a closed system, observable, known limits, etc. Yet Unwin arrives at the bizarre conclusion that “Surprise at the existence of life [in the universe], like surprise at the accuracy of the mall map (in terms of the “You are here” notation) is unwarranted.” This is but the creationists “fine tuned universe” or “anthropic principle” in disguise.
Unwin then shifts to discussion of “irreducible complexity”, another creationist canard wielded against evolution, before expressing his view, “My humble view is that if we wish to ascribe to God…”
Whoa… Wish to ascribe to God? I wish to determine the probability that “God Exists,” not engage in wishful thinking about what we would like God to be if we had our druthers. But I’ll keep reading…
The Dam is Cracking:
I’m reminded at this point of Tim Minchin’s “Storm” in which he says, “A crack begins to appear in my diplomacy dike” and it will soon be unable to hold back the ravings this author deserves.

Unwin again, “I believe that any science-based argument for or against the existence of the person-God is troublesome. Looking for God in science is like breaking open a television set to look for the tiny actors inside.” Need I elaborate on how horribly deficient this analogy is? It’s on par with the equating of God with Cincinnatti… i.e. desiring to talk about the undefined in terms that have meaning. And what discussion of God and science would be complete without a slip into this kind of Gould-esque NOMA stance?
And then the talk turns to Bayesian probability calculations. I’ll be honest: by this point I’ve lost interest in the project, so I flip to the “conclusions” of chapter 4, one of which is to assign a 50% probability of God existing right out of the box. Unwin calls this taking the position of maximum ignorance, and I will have to agree with him… but not in the way he means it. It appears we are going to be adducing evidence for and against God’s existence (as a “person”) and adjusting our ignorance level moving forward. By the end of the Bayesian section, the probability that God Exists is 67%. Spoiler alert. Oh… too late. By my lights, at best Unwin should be at 17%, but NO calculation takes into effect the question of whether or not “God” should have been posited as an explanation of anything at all in the first place.
But it is only arriving at the skimmed-to conclusion of the book that I can fully explode. “Our model indicates that as a consequence of the disparate characters of faith and probability, faith-based beliefs can provide no legitimate basis for any form of human conflict.” Is he denying religious conflict, or simply playing the definitional trump card of “since I define it this way, anything to the contrary can’t be “truly” using the words correctly.” And… enter the no-True Scotsman fallacy.

[Linda · Rating 3 out of 5]

What did I just read? This book seems to be based on some pretty strange math, some almost incomprehensible religious theory and figures pulled out of the air! In the end, God wins. I think the conclusion could have been reached in a more direct way but what fun would that be! God might be something we can’t understand but it doesn’t matter.. we just have to believe.

[Steve Mitchell · Rating 4 out of 5]

If all religious people were as honest and open-minded as this, then there would have been no reason for Richard Dawkins to write The God Delusion.

Also worth a read just to understand how Bayes’ theorem works.

It does get a bit bogged down when he tries to reconcile how faith and the balance of probabilities are linked, but on the whole this is actually a good read even if I disagree with the main point that the book is trying to make

[Nick Woodall · Rating 5 out of 5]

A book based on Bayes Theory of Probability. Well-written with the math explained so that you can understand it. I was very intrigued by this book because I had read a book on Bayes Theory of Probability and really understood the complexity of this book. I highly recommend it!

[Art King · Rating 5 out of 5]

Very original thinking and good bayesian statistics went into this book on probability and God's existence.

[Dani]

I find it unlikely this will,convince a skeptic that god exists - but I finally figure out what I was supposed to be learning in stats class.

[James · Rating 4 out of 5]

A fun book. Two things stand out to me: the main Bayesian part to find the probability of God's existence, and the secondary part about faith making up for probability.

One issue I had with the Bayesian part was, his initial probability (before any evidence). How do we assign this? Atheists often load down theists with a "burden of proof". I would think that would be mathematically expressed in this initial probability. Can an atheist come up with a number that isn't arbitrary, for the theist to overcome? On the other hand, starting with 50%, as Unwin does, seems a bit arbitrary in itself.

There's a kind of anthropic principle to questions about the existence of things. We only end up believing in the things that we begin our (literal or figurative) Bayesian analysis on. Perhaps this makes us weight the existence of (a particular) God higher than we should, given that we're not also considering all other possible gods (or really, other potentially existing entities). So is that how we should calculate the burden of proof modifier to the initial probability? Correct for the existence of many supposed gods or entities, by lowering the percentage? Exactly how many gods or other entities are there, then? There are uncountable entities of which we could wish to assess the existence (if you count every god or entity imaginable, then infinite?). So then we would start with probability 0? But then, because Bayes' Theorem is multiplicative, according to the process in this book (which I take to be a straightforward use of the theorem), nothing exists. It's literally so improbable that any given thing exists that no evidence can convince us otherwise. On the other hand, what if we started with probability "almost 0"? (Assuming that thinkable gods and entities are finite, because there isn't enough time and brains to think of everything?) Then, only a tiny fraction of thinkable things exist. That sounds right. But, what exact "almost 0" number do we choose? So, perhaps we don't want to use that method of calculating the burden of proof.

Of course, maybe the burden of proof, if it's not too close to 0, doesn't matter too much, because all of the evidence dilutes its influence. Unwin runs Bayes' Theorem 6 times. Why not 12 times, splitting each form of evidence into two sub-forms? Why not 1 time, lumping them all into one "evidence"? Perhaps one area of evidence should, for some reason, count more than the others. Unwin did not introduce any weighting. Is there a non-arbitrary way to split or lump categories of evidence, or to weight them? Unwin doesn't claim that his method is objective, but that it reveals the assumptions and thought process of those who work the analysis. All I suppose I would show with this is that there are more places than this book lays bare for either arbitrary mistakes or "non-considerations" (for instance, maybe Unwin himself would have gotten a different number if he'd tried weighting), or for importing sheer preference in evaluating what you want to believe, or not believe. I'm left inclined to believe that atheists believe what they want to believe, and theists believe what they want to believe, and that probably people believe things by mistake that they wouldn't believe if they understood their own thought process, wouldn't want to believe.

It seems that we do end up believing in things that we don't (literally or figuratively) Bayesianly analyze, or analyze in any way. Some things come and get us. Perhaps atheists would want us to only believe in the things that "came and got us", and for them, using this methodology, God doesn't exist, because he hasn't really showed up. This showing up, like the inescapability of sense perception, or, in a different way, "having to get up in the morning for work" or "being in love with that wonderful person", would have to be beyond analysis, either impossible to analyze on some important level (inescapability of sense perception) or something we just wouldn't analyze or analyze away (realities such as "having to get up in the morning for work" or, "being in love with that wonderful person"). Given the danger of believing just what you want to believe, or of constructing a mistaken chain of reasoning to "find what's out there", it seems that the only thing to do, if you're interested in the truth about God, is to wait for God to show up in that unanalytic or immediate or simply unquestioned way, I guess having cultivated the ability to be open to receiving something beautiful without requiring that you get to have it.

[Aaron · Rating 3 out of 5]

The underlying theme of this book is to discuss the probability that God (as understood by the major monotheistic faiths) exists. The primary tool for this is Bayesian probability analysis. The author spends the first few chapters explaining Bayesian probability analysis and then provides a framework in which the reader can input their own assumptions (an appendix even shows how to set this up in a computer spreadsheet application). The author also provides his own answers. By itself this is of minor interest. Things get much better afterwards, as the author discusses how he did not arrive at 100% probability (and, in fact, it is impossible to get to true 100% probability) and therefore faith must make up the difference. Pascal's Wager, quantum physics, and other interesting things are worked into the narrative, as well. Overall I liked the book, though it was hard getting through those first few chapters as the math was a bit heavy for my liking. Still, I found the final argument to be interesting and I'm glad I read it.

[Ish Rishabh · Rating 1 out of 5]

I read this book because the idea of using Bayesian probability to prove or disprove the existence of God was intriguing. Alas, I was disappointed!

The author said that the beauty of maths lied in its requirement to make things concrete and explicit. Yet, all the likelihood figures seem vaguely derived from intuition. Nothing concrete about it. Most of these figures were arrived at by making assumptions which may not be reasonable. For example, assuming that the evidences are independent of each other was too far fetched and the author just conveniently mentioned it without any justification and then rushed into the calculations.

I gave up after the 7th chapter. The reason I am not giving this book a 1-star rating (I am inclined to, btw) is because the way the problem was reduced to a Bayesian formulation was excellent! It was intriguing enough to impel me into reading this book in the first place.

[Angela · Rating 4 out of 5]

This turned out to be more interesting than I was expecting. It's a very clear, understandable introduction to Bayesian Statistics.

It also brings up some interesting questions/ideas about the nature of belief & faith.

I'm guessing the subtitle ("A Simple Calculation That Proves the Ultimate Truth") was a marketing add-on, as the book itself doesn't claim to prove anything - it simply provides a formalized way of considering evidence.

Recommended to pretty much anyone - no advanced math skills or particular beliefs required to get something out of this book.

[Phillip · Rating 4 out of 5]

The author argues this is intended to be a pragmatic and not formal, scholarly argument. That being said, I had to read this twice to get a little use to bayesian analysis.
The math for Bayes is supposedly quite simple, however, unless one has a facility with math, I think parts of this book can be a bit difficult to apprehend, however, it is a useful read for, arguably, the most important question we face as a species.

[lk05321 · Rating 4 out of 5]

A mathematical approach to finding the odds that God exists. Very interesting. I left the book with a greater wonder for God and our universe.

[Amir]

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