The Logic of Atheism


Chuck Doswell

Posted: 27 March 2011 Updated: 07 April 2011: minor revisions

This is my opinion. If you wish to communicate your opinion regarding this topic, you can contact me at cdoswell at - either use the email hyperlink or cut and paste after replacing _at_ with @. However, if you're not willing to have your comments posted here, along with my response, don't waste my time or yours.


1. Introduction

The central element of atheism is the absence of belief in the existence of a supernatural deity of the sort described in the major monotheistic religions (Judaism, Christianity, and Islam). Contrary to many claims by theists, it does not follow logically that atheists share the belief that said deity does not exist. Some atheists may make such a claim, but that belief isn't universally held amongst atheists, who are united only in the agreement of not believing in a supernatural deity. Note that so-called agnostics are atheists who choose not to take the additional step of asserting an absolute belief in the non-existence of a deity. This may seem like hairsplitting, but one essential characteristic of atheists is that their beliefs are all over the place. Discussions among atheists often are characterized by intense hair-splitting and even acrimony! There's no universally-accepted atheist creed, there's no atheist dogma, there are no atheist churches, no atheist liturgy, and there are no texts held to be sacred that define atheist beliefs. Contrary to many claims by theists, atheism is not a religion in its own right -- it's the negation of any religion based on a supernatural deity! Atheists only agree about one thing: non-belief in a supernatural deity.

2. What does it mean to "believe" in something?

From - the most pertinent definitions are indicated in red text:


  1. -verb (used without object) to have confidence in the truth, the existence, or the reliability of something, although without absolute proof that one is right in doing so: Only if one believes in something can one act purposefully.
  2. -verb (used with object) to have confidence or faith in the truth of (a positive assertion, story, etc.); give credence to.
  3. to have confidence in the assertions of (a person).
  4. to have a conviction that (a person or thing) is, has been, or will be engaged in a given action or involved in a given situation: The fugitive is believed to be headed for the Mexican border.
  5. to suppose or assume; understand (usually followed by a noun clause): I believe that he has left town.
  6. -Verb phrase believe in,

a. to be persuaded of the truth or existence of: to believe in Zoroastrianism; to believe in ghosts.

b. to have faith in the reliability, honesty, benevolence, etc., of: I can help only if you believe in me.

Some interesting material there, especially in definition #1, which specifically excludes having absolute proof. If one has absolute proof, naturally, belief is inescapable. Absolute proof is pretty difficult to come by, as I will explore below. To have finite confidence implicitly admits the logical possibility that the belief could be wrong! Consider the definition of faith from the same source:


  1. -noun confidence or trust in a person or thing: faith in another's ability.
  2. belief that is not based on proof: He had faith that the hypothesis would be substantiated by fact.
  3. belief in god or in the doctrines or teachings of religion: the firm faith of the Pilgrims.
  4. belief in anything, as a code of ethics, standards of merit, etc.: to be of the same faith with someone concerning honesty.
  5. a system of religious belief: the Christian faith; the Jewish faith.
  6. the obligation of loyalty or fidelity to a person, promise, engagement, etc.: Failure to appear would be breaking faith.
  7. the observance of this obligation; fidelity to one's promise, oath, allegiance, etc.: He was the only one who proved his faith during our recent troubles.
  8. Christian Theology. the trust in God and in His promises as made through Christ and the Scriptures by which humans are justified or saved.

Arguably the most relevant definition of faith, as I'm seeing things, is #2. Faith and belief are closely intertwined, evidently.

One very compelling way of developing belief in something is via logical proof, as in mathematics. A logical proof is predicated on some set of axioms (assumptions that are not subjected to any standard for proof but which form the basis for a logical system) and some method for manipulating concepts within the possibilities defined by that set of axioms. Many of us encountered this for the first time during high school geometry. Using logic based on this, for example, within the set of axioms associated with Euclidean geometry, it is possible to prove the Pythagorean Theorem. If you grant the assumptions, you must accept the inevitability of the Pythagorean Theorem -- in other words, the proof of the Pythagorean Theorem makes belief in it unavoidable.

Of course, the validity of the axioms are open to question (not sacred!), and it's quite possible to image a non-Euclidean geometry (e.g., geometry on the surface of a sphere), where the theorems may have to be modified to account for a new set of axioms. Mathematical proof is, within its logical constraints, not subject to reconsideration or re-examination. Once a proof has been established, it's for all time. Someone may construct a different proof from the first one, perhaps more "elegant" but the hypothesis remains proven forever after the first proof has been completed and verified to be logically correct.

As discussed elsewhere (e.g., here and here), science does not generally provide such absolute proof. Scientific understanding is always provisional and open to reconsideration. Hence, the very notion of "scientific proof" is an oxymoron. There's no "proof" of anything in science that even remotely compares to the absolute solid permanence of mathematical proofs. Nevertheless, some scientific ideas (the Laws of Thermodynamics, the Law of Gravity, the Theory of Relativity, the Laws of Quantum Mechanics) have been so thoroughly tested and confirmed by all those tests that they may seem immutable and proven beyond question. That would be a misunderstanding of science, however, as these ideas may yet be superceded in the future.

Despite the apparent volatility of its ideas, scientific understanding has proven to be very useful when applied to the real world. For example, although Einstein's Theory of General Relativity is widely accepted as having superceded the Newtonian Law of Gravity, NASA still uses Newtonian physics to guide their spacecraft about in the solar system with remarkable success. In order to have their spacecraft succeed in their missions, it's just not necessary to complicate Newtonian physics with the subtleties of Einstein's relativity concepts. The notions of Einstein have supplanted those of Newton in an abstract sense, but in the pragmatic world of guiding objects through space on long journeys between worlds, Newtonian physics continues to be quite accurate and effective. Relativistic corrections of Newtonian predictions are trivial at the speeds available to existing spacecraft!

3. Evidence based on "sacred" writings?

If scientific "proof" is never absolute and absolute proof is only a logical abstraction, what's left? Let's consider the issue of the existence of a supernatural deity, the fundamental point of conflict between atheists and theists. Given that absolute proof is not possible, on what basis might one choose to accept the existence of a deity on the rational basis of a preponderance of the evidence?

If we wish to consider the content of the sacred texts of the monotheistic religions as "evidence", a number of issues regarding those documents must be recognized:

Therefore, these "sacred" documents are essentially of no value in establishing the historical or scientific veracity of the events described therein. They don't describe the results of scientific experiments, they don't offer hypotheses about how the natural world works, they don't constitute a science textbook, nor do they even meet reasonable criteria for a history textbook.

To the limited extent that these "sacred" writings intersect science, it's evident that their content is nothing more than mythology and superstition. Their "explanations" of events explain nothing -- attributing something in the natural world to a supernatural deity constitutes no explanation at all. This is the ultimate deus ex machina, in fact! The extent to which they've been written and/or inspired by the wishes of a supernatural deity is essentially unknown and unknowable, but given the inconsistencies and internal contradictions, the authorship or inspiration of an omniscient and omnipotent being seems pretty implausible. Hence, they cannot be considered credible in their own right unless one accepts the sacred origins of their content solely on faith (i.e., without evidence). Thus, their content can provide no evidence for any rational, evidence-based argument.

Some of the people mentioned in these texts are historical figures, whose existence has been or can be confirmed by archeological investigations. What the bible has to say about such historical figures may or may not be accurate. However, the central figures of the so-called New Testament (e.g., Jesus) are not historically-validated. That is, there's no independent historical evidence to support all of the (sometimes inconsistent or contradictory) accounts given in these sacred texts.

Strict reliance on the accounts given in religious documents is basically not even remotely credible by any reasonable standard of scientific evidence in support of the historical events described therein. It's just not possible to use these "sacred" documents to validate anything by any reasonable, rational reasoning process.

4. Logical counter-arguments

Atheists frequently make the assertion that it's impossible to "prove" a negative proposition. The basis for such an assertion is that no matter how implausible some hypothesis might be, to show that it's absolutely not true would require a comprehensive knowledge of everything for all time, which is clearly impossible. For instance, I might postulate a being made up entirely of a plate of spaghetti and meatballs that has created us and the universe; apparently, a pretty powerful pasta dinner. To show that such a being absolutely does not exist, I would have to show by some logical argument that such a being is in fact impossible. Such a demonstration is evidently well beyond my capabilities, despite the clear evidence that it's pretty much unlikely. You can argue, for instance, that no plate of spaghetti and meatballs has ever even shown any sign of being capable of thought, let alone the ability to create the universe. However, such an argument is empirical rather than logical -- that is, it's based on existing evidence. There may be a pasta dinner plate somewhere in the universe that is sentient and in fact is omniscient and omnipotent. To say that an omniscient, omnipotent pasta dinner is impossible is to claim your own omniscience, at the very least -- and it's not clear how you would know such a thing as fact. Unfortunately, no human being can make such a claim legitimately. This hypothetical being must remain a logical possibility, no matter how absurd it might seem. I just can't "prove" logically that such an all-powerful dish of pasta and meatballs doesn't exist somewhere!

Of course, it can be quite possible to "prove" some sorts of negative statements, provided the standard of "proof" is not absolute. Suppose I postulate that the President of the United States is a being made up of a plate of spaghetti and meatballs. Given that many of us followed the election of Barack Obama as President of the United States, and we regularly see broadcasts of his news conferences and various Presidential activities, it would be reasonable to consider this an empirical demonstration of the negative: the President of the United States is pretty evidently not a being made up of a dinner of spaghetti and meatballs, although it's likely he's eaten such a meal (perhaps many times). Unfortunately, common, everyday experience is not even up to the standards of scientific evidence (such experience would be described as anecdotal evidence), so it's quite far from a purely logical argument capable of providing absolute proof. Nevertheless, many of us accept our own personal experiences as pretty compelling evidence that the US President is not a being made from a plate of spaghetti and meatballs.

One logical possibility is that we could all be Trumans, living a life that is actually an elaborate hoax perpetrated on us by someone or something -- a vast conspiracy aimed at fooling us into accepting a complicated illusion as reality. I would feel very sorry for someone laboring under such a notion, but it must remain a logical possibility since I can't "prove" it's not true. The trick about logical possibilities is that many of them can be absurd (as is my example about the spaghetti dinner President), but it generally is not possible to rule them out via some absolute proof using logic alone! My inability to prove absolutely a negative proposition (i.e., a supernatural deity does not exist) does not equate to a logical necessity to accept the counter-proposition (i.e., that a supernatural deity does indeed exist)!

5. Miracles as evidence

Proponents of a supernatural deity, on the other hand, have accepted (mostly on faith passed on to them by their religious teachers) the hypothesis that this postulated being exists. In the times that the putative sacred texts were written, supernatural events seemingly were more or less commonplace: two millenia ago, Jesus walked on the water, he turned water into wine, raised people from the dead, fed the multitudes on five fishes and two loaves of bread, etc. The deity of the Old Testament spoke to prophets in the late Bronze age via burning bushes (that weren't consumed), parted the waters of the Red Sea, turned Lot's wife into a pillar of salt, and so on. Assuming that these events were what they're claimed to be (rather than pure fictional fabrications, illusions performed by deceivers, or misinterpretations of natural events by late Bronze age peoples not far removed from being nomadic hunter-gatherers), they would constitute compelling evidence for the existence of a deity capable of violating the very laws of the natural world that he/she/it created in the first place!

If I'd witnessed just one such miraculous and obviously supernatural event of the sort described above, I'd have become a believer instantly. Unfortunately for me, and all the rest of us living at present, it seems we no longer have the luxury of seeing miracles performed or having the deity speak to us. In fact, our deity at present seems hell-bent on avoiding any overt evidence of his/her/its existence! Why the change of heart? What divine purpose is revealed by this stubborn reluctance to provide incontrovertible evidence for his existence in this day and age? Unlike the citizens of biblical times, we're required to accept this whole schtick on faith! The justification is that the deity works in ways unknowable to us. Why didn't he create us to be smart enough to understand the reasons for the things he does? Why would a creator value the adoration of people he created to be incapable of grasping what he's up to? Sorry, that makes no sense to me!!

6. The voice of the deity

Again, in the biblical past, the deity spoke with people frequently, in addition to performing supernatural feats. Although the deity couldn't reveal himself to mere humans as it seems his splendor would have disintegrated them on the spot, he managed to communicate with many biblical prophets from time to time, at least in the Old Testament. If one assumes that Jesus of the New Testament was, in fact, one and the same with god the father (and the holy spirit), then the deity was just blabbering on with folks all the time for decades. But following the resurrection and ascencion of Jesus, now the conversation is all one-way, apparently.

Of course, many people in the present era claim to have heard the words of some supernatural being. Some of them go on to found cults of followers. But it's generally acknowledged that people who claim to have heard directly from some supernatural deity either are lying or simply are not sane! Hearing voices in one's head is symptomatic of paranoid delusions, not divine intervention. People have murdered others because they felt they were commanded to do so by such voices (or by religious leaders making the claim of having heard the voice of the deity). This is not evidence for the existence of a supernatural entity, but simply the hallucinations of people who have succumbed to irrationality, perhaps as a result of some chemical imbalance in their bodies!

And various religious fanatics occasionally claim to have received "signs" from their deity about what to do. Since straightforward conversations with the deity no longer take place, for mysterious reasons known only to said deity, believers have to interpret events as indicating their deity's will. This can have interesting or even sinister interpretations.

But aren't monotheistic religions based on irrational faith rather than evidence? Some people choose to interpret natural events as evidence for their chosen supernatural deity. Since prehistoric times, people have seen various natural hazards as the wrath of their chosen deity for putative misdeeds by the people. Although no one can "prove" in an absolute sense that these events are not the actions of a deity enraged by our defiance of his/her/its laws, science now offers a very different view of them: these are natural processes, indifferent to the havoc they may cause humans as the Earth responds to natural forces we humans are quite capable of understanding. We have no evident need to postulate a deity to explain natural hazards because rational science has moved beyond mythology!

7. Evidence for the non-existence of a deity?

What sort of evidence might one be able to muster for the non-existence of a particular supernatural deity? Several folks have compiled whole books (e.g., here and here) and developed websites designed to show the "evidence" against the existence for the supernatural beings described in monotheistic religions. I applaud such efforts, as they constitute a major reason why someone should be skeptical about the deities proposed in the major monotheistic religious cults (Yes, I consider them cults!). But they fail to attain that impossibly high bar of absolute proof (of the sort embodied in mathematical, rather than scientific, "proof" standards). Thus, it remains the case that the existence of the postulated deity is at least a logical possibility. You could characterize my atheism as being of the agnostic variety, as I'll explain below.

But consider the pragmatic, relatively attainable standard of scientific evidence. The Law of Gravity first proposed by Isaac Newton has been mentioned as an example of how scientific evidence can be pretty compelling, even if it's not absolute proof. Suppose you were to dispute the Law of Gravity on purely logical grounds. How confident would you be that you could, for instance, hurl yourself off a precipice into a canyon two hundred meters deep and yet gravity would not operate on you according to Newton's Law of Gravity so as to dash your fragile body on the rocks below? In Quantum Mechanics, extremely unlikely events on a large scale are considered possible, although at very, very low probability. Hence, by pure logic, it's possible you could survive the experience of throwing yourself off a cliff (without a parachute, of course), but it's extremely unlikely! So unlikely as to render it pragmatically impossible, even if the logical possibility of survival still exists.

If you believe in a deity who blesses you with faith in him/her/it, then perhaps you would trust that your deity would intervene on your behalf when you jump off that cliff. Just how confident are you that your deity will act to prevent your death? But wait! If that deity were to perform such a "miracle", that would constitute stunning new evidence of his/her/its existence! Unlike in biblical times, your deity apparently is unable to intervene because it would give away his/her/its existence (Exactly why is this forbidden, now? The reason for this change is not very clear.). Too bad for you, though -- despite your unwavering faith, the outcome is almost certainly your demise on the rocks at the base of the precipice. Masking his/her/its existence apparently trumps saving you, but at least you get to go to heaven and live in eternal bliss in compensation for your faith. But wait! Isn't suicide a mortal sin? Oops! Sorry, but you're set to live out the rest of eternity in torment for the sin of killing yourself. But your deity loves you!! Perhaps you wish to conduct this scientific experiment yourself as a test of your faith? Show me how sincerely you believe in your deity!

8. Where does this leave things?

Although people can choose to interpret events however they wish in a free society (Theocracies are almost universally intolerant of interpretations they haven't sanctioned!), it seems to me that although the evidence against the existence of a supernatural deity is pretty strong, it falls short of absolute proof, and always will. If this deity relents and starts allowing miracles and speaking openly to us again, we might then conclude that such demonstrations constitute pretty extraordinary evidence of this deity's existence. Asking for evidence of extraordinary claims doesn't seem to me to be such a bad thing. We scientists do it all the time as a matter of course. After all, it's only clerics and other believers who are proposing the existence of an all-everything supernatural being. It might be presumptuous to ask a deity for evidence, but why not when a human does so? The clear conclusion, since they inevitably begin to rationalize why they can't do so, is that these humans simply are unable to provide such evidence! All they can offer are excuses and pseudo-explanations for their lack of proof.

Scientific standards of evidence allow us in some cases to act as if absolute proof has been demonstrated, even though it has not, in purely logical terms. Thus, the example of the Law of Gravity shows us a standard of evidence that permits us to assume this law is absolutely true, even though we have to admit logically that absolute proof of the Law of Gravity has not been achieved.

In the absence of compelling evidence for the existence of a supernatural deity, and the vast accumulation of evidence that indicates strongly the lack of any necessity for accepting the "God Hypothesis", it seems to me that I can act as if I believe that your supernatural deity doesn't exist, even though I have to admit to an extremely low probability that I could be wrong. That is, when I behave as if I believe that a supernatural deity doesn't exist, I'm really saying that on the evidence I now have, I can only believe in that non-existence as a provisional hypothesis. It's not a matter of faith, equivalent to believing in such a deity, at all. If such compelling evidence as I've described can be shown to demonstrate the existence of a supernatural deity, then I'll change my opinion. This is what scientists do. This is how rational arguments based on logic work. In exactly the same way that I "believe" in the Law of Gravity, I "believe" that a supernatural deity doesn't exist. Faith has absolutely nothing to do with that conclusion! If it were based on faith, then I would simply close my mind to any argument, which is what stubborn believers do -- nothing rational could ever serve to change an opinion based entirely on faith.

The "sacred" texts of the monotheistic religions are laced with logical inconsistencies, contradictions, and outright errors about historical events. These documents are incapable of providing a logical, scientific, historical basis for any rational debate about the deities they purport to describe or the religious dogma they present. Where is the objective evidence outside of these texts for the existence of a deity? In the complete and utter absence of such evidence, the logical necessity is to reject that hypothesis -- until such a time, if ever, that strong evidence for the existence of a supernatural deithy can be offered and considered in a rational debate. In rational debate, extraordinary claims demand extraordinary evidence, so anyone claiming to have "proven" the existence of a deity must provide some very compelling results, indeed! My choice not to believe in a supernatural deity is consistent with the existing absence of such extraordinary evidence, whereas belief in the existence of the putative deities of the major monotheistic religions is inconsistent with the evidence now available.