Burden of Proof

Expose False Symmetries & Weed Out Spurious Arguments


When two opposing points of view confront each other, it must not be assumed that they are symmetric, i.e. that they are both about equally plausible. That may sometimes occur, but often one side is much less plausible than the other. When one side of the debate is highly implausible and extraordinary, then the burden of proof falls on those who advance that side.

Sommaire en français Lorsque deux points de vue opposés s’affrontent, il ne faut pas supposer que la situation est symétrique, c’est-à-dire que les deux côtés sont à peu près également plausibles. Cela peut parfois se produire, mais souvent l’un des deux côtés est beaucoup moins plausible que l’autre. Lorsqu’un côté du débat est hautement invraisemblable et extraordinaire, le fardeau de la preuve incombe à ceux qui avancent de ce point de vue.

The concept of burden of proof is an important logical tool which allows us to weed out spurious arguments. It does so by exposing the falsehood of alleged symmetry between two opposing arguments or, in some cases, completely inverting the apparent plausibility of the two opposing sides. We say that one of the opposing sides has the burden of proof when they are making a specific assertion which requires substantiation, whereas the other side is simply expressing scepticism.

Those who take an irrational position, whether out of ignorance, confusion or dishonesty, generally fail to take account of this aspect of the debate. Sometimes they argue for symmetry in a situation where in fact there is no symmetry between the opposing sides of the debate. Worse, they may assume, sometimes unconsciously, that the burden of proof falls on the wrong side.

The basic idea here is summed up in several famous quotations. Science educator Carl Sagan, in his famous television programme Cosmos, declared that “extraordinary claims require extraordinary evidence.” The statement by Christopher Hitchens that “what can be asserted without evidence can also be dismissed without evidence” has become known as Hitchens’ Razor. The ancient Greek mathematician and geometer Euclid made a very similar statement, “what has been affirmed without proof can also be denied without proof”, more than two millenia before. Thus, the burden of proof falls upon the person who makes some extraordinary claim. The opponent who merely questions that claim has no such obligation.

I will illustrate using the following three examples.

(1) Does “God” Exist?

An individual claims that “God” exists. However, another individual disagrees, claiming that knowledge of the existence of such an entity is unavailable. Clearly, the burden of proof here falls upon the person making the claim of god’s existence, starting with the obligation of defining what they mean by “God.” In the absence of such definition or proof, anyone who disagrees may simply dismiss the claim and is under no obligation whatsoever to prove the non-existence of the hypothetical god proposed by the claimant. There is no symmetry between the god-hypothesis and the rejection of that hypothesis. In other words, there is no symmetry between theism and atheism.

(2) What Does “God” Say About Sex?

An individual claims to know what “God” wants in some situation. For example, the individual may claim that god abhors sexual behaviour other than heterosexual relations between a man and a woman who are legally married to each other and that all other sexual behaviour is forbidden. However, another individual disagrees, claiming that no such rule is known to apply. Which individual is right? Clearly, the burden of proof falls upon the individual making the assertion about the will of “God” because that assertion requires knowledge of the existence of god, knowledge that god has a will and knowledge of that will itself. Unless the first individual offers some proof in support of their claim, those who disagree may simply dismiss it. There is no symmetry between the two sides of this disagreement.

(3) Do Symbols Communicate Anything?

A government introduces legislation which bans civil servants and public schoolteachers from wearing religious symbols while on duty. Opponents of the proposed law claim that the ban is unnecessary because, in their opinion, such symbols have no significant effect either on users of civil services or on public school pupils. Supporters of the law disagree. On which side should the burden of proof fall? This situation may appear less obvious that the previous two. Perhaps we have a symmetrical situation here, where the competing assertions are about equally plausible, where neither claim is extraordinary?

However, upon closer inspection, any apparent symmetry disappears. Why do some religious believers wear religious symbols? They do so to communicate their religious identity to others, i.e. in order to assert that identity ostentatiously. If such symbols had no effect, believers would not wear them. Pious Christians use the verb “witness” to describe the act of asserting one’s Christian identity by word or by symbol. Why do corporations spend enormous amounts of money on advertising, using symbols, logos, slogans, etc. to promote their products and/or their brand? They do so because advertising works, because such displays influence those who are exposed to them and change their behaviour in some way.

Thus, It is eminently reasonable to expect that religious symbols will have a real effect on those who witness them. Furthermore, we can expect a particularly significant effect if the wearer is a civil servant or schoolteacher on duty, especially if the observer is a child. In fact, some forms of advertising directed at children are forbidden by law, and for good reason. To assert that such symbols would have no effect—or only harmless effect—is an extraordinary claim which can be rejected in the absence of proof of such innocuousness. A precautionary attitude requires that we take the potential effects of religious symbols seriously.


Of course, some extraordinary claims may turn out to be valid, but only if solid supporting evidence is provided. But in the three examples given above, the claimants never succeed in providing such evidence for their extraordinary claim.

Next blog: Sur l’extrémisme trans

Carl Sagan’s Achilles’ Heel


On the occasion of the recent 20th anniversary of Carl Sagan’s death, I discuss and criticize his refusal to reach the necessary conclusion of atheism.

Sommaire en français Pour marquer l’anniversaire récent de la mort de Carl Sagan, je commente et critique son attitude à l’égard de l’athéisme et son refus de cette conclusion nécessaire.

The 20th anniversary of Carl Sagan’s death occurred very recently—20th December 2016—and was celebrated by many, in particular by those who have strong interest in science and the promotion of scientific literacy, critical thinking, skepticism, etc. His life and work is very justifiably honoured as he was one of the great popularizers of science, perhaps the greatest of the late 20th century.

However there is one aspect of Sagan’s approach to science and skepticism which is largely overlooked and merits closer consideration. The anniversary date issue of eSkeptic, an email newsletter from the Skeptics Society, was dedicated to Sagan’s memory and included a number of quotes from his works. One quote in particular stands out:

On Theism & Atheism

Those who raise questions about the God hypothesis and the soul hypothesis are by no means all atheists. An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed. A wide range of intermediate positions seems admissible, and considering the enormous emotional energies with which the subject is invested, a questioning, courageous and open mind seems to be the essential tool for narrowing the range of our collective ignorance on the subject of the existence of God.

“The Amniotic Universe,” in Broca’s Brain

The major flaw in the above declaration is the assertion that “An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God.” The validity of the first half of that assertion depends critically on the meaning of the word “certain” while the second half is a serious misrepresentation of atheism.

Consider the first half: “An atheist is someone who is certain that God does not exist…” If Sagan interprets certainty as meaning absolute certainty, then this is a caricature of atheism. Atheism is based on the scientific (not absolute) certainty that all theisms are false, that is, the falsehood of theism is certain beyond any reasonable doubt. Religions deal in absolute certainty and claim to possess it. But science is realistic. Absolute certainly is rarely if ever achievable and it is not necessary. An infinitesimal probability of falsehood is sufficient in order to draw a realistically certain conclusion.

There is no credible evidence for the god hypothesis; indeed, so-called proofs of the existence of god rely primarily on the argument from ignorance which is basically equivalent to the god of the gaps—i.e. we don’t know how it came to be, therefore god did it, which makes as much sense as saying “I don’t know why I cheated, therefore the devil made me do it.” Furthermore, the birth of god-beliefs in prehistoric and ancient times is readily explained by human psychology and our nature as a social species. Finally, theism is riddled with internal inconsistencies and self-contradictions which destroy its credibility even without reference to questions of evidence. See, for example, my talk, The Will of God: Pure Fiction.

Compelling evidence of non-existence is NOT required.

Now consider the second half of Sagan’s assertion: an atheist is “someone who has compelling evidence against the existence of God.” Compelling evidence of non-existence is NOT required. Sagan himself is famous for repeatedly insisting that “Extraordinary claims require extraordinary evidence,” an observation which recalls Euclid’s famous “What has been affirmed without proof can also be denied without proof.” Few claims could be more extraordinary or more lacking in proof than the god-hypothesis. The considerations listed above are sufficient to reject that hypothesis. Counter-evidence is not required.

The bottom line is this: atheism is the logical, scientific conclusion to a full consideration of the pretensions of theism. There is no room for reasonable doubt, no reason not to take that final step from agnosticism to atheism. For further discussion, see my AFT blog Why We Are Not Agnostics.

To his credit, Sagan was apparently not a symmetric agnostic, at least not according to Joel Achenbach’s discussions of Sagan’s views in Carl Sagan denied being an atheist. So what did he believe? [Part 1] and Why Carl Sagan is Truly Irreplaceable. (Although in the quote given above, Sagan speaks of the existence and nonexistence of “God” as “confident extremes,” as if there were symmetry here.) Symmetric agnosticism is a very dogmatic stance, occupying a middle ground resolutely centred between theism and atheism, putting the two on an equal footing and thus assuming—completely gratuitously—that theism has a 50% probability of being correct.

Symmetric agnosticism is a very dogmatic stance, occupying a middle ground resolutely centred between theism and atheism, putting the two on an equal footing …

However, even though Sagan leaned towards atheism, his failure to take that final step validates and comforts theistic beliefs. Even if Sagan completely rejected Judaism, Christianity and Islam (the three Abrahamic monotheisms), his agnosticism, his continued hedging on the ultimate question of atheism allows religious apologists to continue to peddle their nonsense with a minimum of intellectual opposition.

Such waffling has consequences. The skeptical movement has been infested with this mentality for far too long. For example, at its 2006 AGM, the organization Les Sceptiques du Québec (S.d.Q.) removed from its declaration of principles the mention of “secularism” (“laïcité”) which had been added the previous year. Why? Well, mainly because the proponents of the addition of secularism to the organization’s principles in 2005 were atheists, and the leadership of the organization was dominated by symmetric agnostics (and may still be, as far as I know) who displayed a total mistrust of up-front atheists. I emphasize that the principle removed was secularism, not atheism.

That an association which claims to promote scientific skepticism could refuse to endorse secularism is outrageous. If one does not support secularism, then one must be willing to accept compulsory religious instruction for children in public schools, instruction in the dogma of any religion such as Christianity, Scientology, Shamanism, or whatever. This decision by S.d.Q. was an example of intellectual inconsistency and cowardice, rationalized by a dogmatically agnostic worldview. An organization with such a pro-religious bias has failed to live up to its claim of being skeptical.

Of course my criticism of Sagan does not in any way reduce his considerable accomplishments. I am simply adding an important aspect to help complete the picture we have of him. Just as we can aspire to emulate him in his achievements, we can learn from his mistake with respect to atheism and do even better.

Next blog: More Dubious Words



Welcome to my personal blog. This is my first, introductory post, setting forth the main themes which I wish to explore and why I have chosen them.
Sommaire en français Je présente non nouveau blogue personnel qui sera dédié à l’athéisme et la lutte contre l’obscurantisme religieux et contre les croyances surnaturelles. Je m’intéresse particulièrement aux façons dont les incroyants eux-mêmes se laissent malheureusement distraire par des idées reçues et des préjugés populaires et agissent parfois contre leurs propres intérêts. Ces distractions sont souvent le résultat d’une mentalité religieuse — surtout l’athéophobie — mais ce n’est bien sûr pas la seule source des erreurs. Vous pouvez aussi lire de mes écrits sur les sites web LPA et AFT, mais dans ce blogue personnel je sortirai parfois du cadre des questions pertinentes pour une association athée.
The principal — but not necessarily exclusive — theme of my personal blog will be atheism and the struggle against religious obscurantism, because these are the issues that interest me the most, as well as concerns directly related to these issues such as secularism, freethought, critical thinking, rationalism, scepticism, humanism, etc. In particular, I expect to devote much of my attention to exposing and criticizing atheophobia in its myriad forms. My intent is to explore ways in which non-believers often act or speak in ways which are contrary to their own self-interests, because they have let themselves be influenced and distracted by prejudices and pre-conceived notions which are prevalent in society and have distorted their perceptions of the world. Of course, when we are dealing with atheism, the greatest distraction is the unavoidable and all-encompassing religious mentality — the idea that religious beliefs and practices are somehow essentially good and normal, indeed even necessary for morals and ethics, and that harm is done by religion only when it has somehow been debased or misused — a mentality which is ubiquitous in our society and in which we are all awash. In particular, the prejudice against atheism and against atheists — which I call atheophobia — is the most serious of these distractions, causes the greatest damage and therefore must be the first target of criticism. But it is not the only widespread prejudice which compromises the fight against religious obscurantism. You may be familiar with my writings which often appear on the web sites of the organization Atheist Freethinkers (or Libres penseurs athées) of which I am currently president. Why have I decided to start a personal blog when I can express my opinions through the web sites of that organization? There are several reasons. I expect to express myself here on a wider range of issues, possibly diverging from the field of topics which would be relevant for an atheist organization. I may wish to touch occasionally on more personal concerns. Furthermore, I have a lot to say and I do not want to monopolize the AFT and LPA sites, because other members need to express themselves too. Many of these personal blogs will be in English. Some will be in French. I will in general not attempt to be thoroughly bilingual. (This is another reason for this personal blog: the AFT and LPA blogs are bilingual, at least always have been so far, which makes them more laborious to prepare.) I do however plan to include a brief summary of each personal blog in the other language.
  1. Atheism is a scientific certainty, beyond all reasonable doubt.
  2. Religion and science are utterly incompatible.
  3. Religiously based morality is in general corrupt …
  4. There is no symmetry between atheism and theism.
The general, mainstream attitude towards religion is that it is basically a good thing, or at worst neutral, and that it becomes truly harmful only when distorted or misused by fundamentalists or extremists. I consider this approach to be completely wrong-headed and dangerously complacent for the obvious reason that any worldview based on a falsehood must have harmful consequences sooner or later. In other words, religion is basically harmful but can be rendered approximately anodyne and inoffensive by diluting it with generous doses of reality. But supernaturalism always remains there in the interstices, waiting to rear its ugly head and make religious belief pernicious once again. Thus, when writing about atheism and religious obscurantism, I will inevitably engage in much criticism of religion and my approach will of course be anti-religious. However, I do not expect to direct my attentions principally to religious fundamentalism, extremism or radicalism, although those topics are certainly not excluded. Others have already dealt effectively with them and have exposed the intellectual vacuity of such ideologies. My focus will be rather more on how religious attitudes, or perhaps more accurately meta-religious attitudes, are internalized and expressed by those who are ostensibly more moderate — such as so-called liberal Christians for example — and even by those who claim to be our allies in freethought and rationalism but who sometimes betray their own, and our, principles. Acting against one’s own best interests is an extremely widespread phenomenon, so common as to be banal, and it is especially common when dealing with religion and irreligion. There are women who embrace misogynistic ideologies — for example any woman who willingly wears an Islamist veil. There are gays who willingly support homophobic religions, or who support currents such as some variants of “moderate” Christianity which have in recent years toned down their homophobia but maintain the life-denying worldview which gave rise to that prejudice in the first place. There are non-believers who foolishly participate in the denigration of atheists or atheism as intolerant or dangerous, thus implicitly denigrating themselves. There are those who claim to support secularism but oppose it in the very place where it has a serious chance of being formally adopted. As widespread and banal as these behaviours may be, they nevertheless remain irrational and must be criticized. I define “religion” as supernatural religion, i.e. always including a belief in supernatural agents or phenomena which inhabit or emanate from some hypothetical — indeed, fictitious — domain beyond our real, material world. There are other definitions of religion but they only serve to confuse the issue. The issue is supernaturalism. Finally, since my principal topic of discussion will be atheism from an anti-theistic perspective, I conclude by summing up some of the basic underpinnings of my point of view. These are NOT assumptions. Rather they are conclusions which are already well established in numerous books and articles which are widely available. If you have not yet grasped any one of the following points, then you will not understand my blog because you have not done your homework.
  1. Atheism is a scientific certainty, beyond all reasonable doubt. I am not talking about absolute certainty here, as religions often do. I am referring to a very solidly based conclusion which is falsifiable but has never been falsified. All theisms and supernatural hypotheses have been found to be completely baseless.
  2. Religion (i.e. supernatural religion) and science are utterly incompatible. This can be seen as a consequence of the first principle. Or it can be derived from examining the concepts of faith on the one hand and philosophy of science on the other.
  3. Religiously based morality is in general corrupt because it is based on false supernatural beliefs. Morality is a product of our biological and cultural evolution as human animals. Theistic morality is a corruption and perversion of that natural morality. It is thus a gross understatement to say that religion is not necessary for morality; indeed, it would be more accurate to assert that the abandonment of supernatural beliefs is a prerequisite for moral maturity. Religious believers are capable of acting ethically in spite of their supernatural beliefs, to the extent that they set those beliefs aside and do not allow them to interfere unduly with their behaviour.
  4. There is no symmetry between atheism and theism. Anyone who claims that atheism is a kind of religion or faith is either ignorant or intellectually dishonest, and probably both. Any attempt to put atheism and theism on an equal footing is as ridiculous and unethical as putting the victim and the perpetrator of a crime on an equal footing by claiming that both are equally guilty. Theism is an insult to human intelligence. Atheism is a refusal to accept the nonsense which is theism. (There is however one and only one context in which equality is appropriate: when dealing with human beings; i.e. in order to respect freedom of conscience of all persons, atheists and theists deserve equal treatment before the law. But there is no equality or symmetry between the ideas of atheism and theism.)

Next blog: “Secularism Betrayed, Part I