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The Importance Of Understanding Evidence

Why this article?

Central to the debate between theists and atheists, and to our understanding of the world, is the question of how we discover what we can discover and know what we think we know. For this the key issue is evidence.

I approach this topic having spent a career in the law, where evidence is of central concern when it comes to settling disputes.

Inevitably I am focussing on the Abrahamic god idea in this article. Other god notions such as the Spinozan, pantheist or Wiccan concepts of god, or polytheist god ideas may need other examples or approaches but the basic principles remain.

Of course, atheists do not accept that any evidence of the natural world could demonstrate the existence of an alleged supernatural entity or phenomenon, such as ‘god’ is claimed to be. This is an insurmountable problem for theists. If a god could be demonstrated by evidence then that god would be a natural phenomenon, but theists tend to say their god is supernatural and unknowable, and therefore unprovable. Which is why, ultimately, they tend to rely on faith.

In atheist discussions we are often heard to say there is ‘no evidence’ of a god. But how accurate is this?

We need to be highly cued in about what counts as evidence, what is good evidence and what is bad evidence. This way we can head off bad theist arguments at an early stage. We want to focus on their best arguments (if we can spot any).

What is evidence?

Evidence is some fact, statement or thing that helps us determine the truth or otherwise of another fact, a claim or allegation.

What types of evidence are there?

  • the oral evidence of witnesses, including confessions;
  • written documents, including maps, graphs, etc;
  • ‘real’ evidence (for example, objects like the knife used in a stabbing), coins, inscriptions, archaeological evidence, fossils;
  • Expert, scientific and opinion evidence;
  • Photographs and CCTV;
  • Computer generated evidence

Some of these are primary evidence witnessed by those who had first-hand knowledge of the facts, or they are objects which are in themselves pieces of direct relevant evidence.

Other types of evidence are secondhand or hearsay.


Any evidence must be understood alongside its credibility before any piece of evidence is considered.

Credibility is about how believable a piece of evidence is, given the world we live in and the laws of physics, etc., we are all subject to. A mundane fact could be my claim that I am wearing a watch on my left wrist. This is a commonplace thing which is eminently believable and verifiable.

By contrast the claim that a virgin gave birth contradicts everything we know about how the human body works. Although virgin birth, or parthenogenesis, is not unknown in the animal world; virgin birth has not been demonstrated to occur in the human world. Such a claim therefore requires compelling and high-quality evidence to get over the line of credibility.

Also under the question of credibility is the important question of why this witness is giving the evidence or the motivation of the witness in creating the document under consideration.

Further, under the question of credibility is the thorny question of the witness’s honesty and character. A change in the UK criminal law has arguably influenced prosecutors not to embark on prosecutions where the complainant’s character (including previous convictions) makes the testimony of the complainant, as a witness, less believable to a jury.

I now focus on hearsay in documentary form, because that is one of the main types of evidence relied on by theists.

Hearsay including scriptures

Right at the heart of legal thinking about evidence is the problem of hearsay evidence, whether oral or written, for instance, the Gospels and the Quran, are obvious examples.

Hearsay is secondhand testimony when the witness makes statements not about what they have themselves witnessed, but about what he or she has heard from another person who is not present to confirm the statement and be questioned about it. That other person, from whom they have heard the evidence, may themselves also have heard it from another person or source, and the testimony may therefore be third hand or ‘multiple’ hand hearsay. Anyone who has played the game ‘whispers’ (called ‘telephone’ in the USA) will readily understand how unreliable hearsay evidence is.

Examples of multiple hand hearsay are religious traditions handed down orally for some time before being committed to writing. The likelihood of errors and distortions creeping in under these circumstances is not just great, but inevitable.

As each transmitter of the evidence handles the story they are likely to be influenced by their understanding of that story, their hearing or their perceptions of it, and indeed their own culture. Worse, some transmitters will have been moved by their strong beliefs to ‘improve’, ‘correct’, select, emphasise or de-emphasise passages, or generally edit the evidence. All these changes distort the original message or text. This is a universal problem, but was especially rife in the ancient world, where there were limited facilities for fact checking.

Ancient documents are particularly problematic because before the age of printing, manuscripts had to be copied by hand and this inevitably resulted in copying errors, which were compounded over the centuries. Documents will have been copied by scribes hundreds of times after they were written.

Later scribes sometimes noticed what they thought were errors by earlier scribes and ‘corrected’ them, thereby often introducing further errors. Later scribes also interpreted notes written in the margins of the manuscript they were copying and thinking they were part of the text, incorporated them. There are thousands of copying errors in the Bible, and thousands are also being found in the Quran.

Even when printing was invented and used, mistakes are still found. The most famous example is the ‘Wicked Bible’ printed in 1631 which had to be withdrawn when it was found that the word ‘not’ had been omitted from the Commandment in Exodus 20.14 ‘Thou shalt not commit adultery’.

On top of that the original books of the Bible were written in languages which were then translated; the process of translation is not straightforward. The translator needs to decide what they think the passage means, even though the original passage may have been obscure. Distortions are generated by the different cultural meanings attaching to words in different languages, so there cannot always be one to one correspondence of meanings between different languages. This problem is seen especially in the Quran where experts have found a substantial percentage of the Arabic Quran to be ambiguous or obscure.

The gospels were not written by authors claiming to be witnesses of the events they describe. Indeed, the names ‘Matthew, Mark, Luke and John’ were given to the gospels by later tradition; no one bearing those names can be shown to have written them. No manuscripts exist that are signed by the alleged author. The gospels are therefore hearsay; they appear to be the written versions of accounts handed down to the authors. The likelihood of error therefore is substantial, even assuming, (which cannot necessarily be assumed), that there was a truthful and accurate core originally.

Perhaps a symptom or product of these problems is the fact that there are discrepancies between the various gospel accounts. Entire websites deal with this problem:

Biblical scholars have also concluded that the authors of Matthew and Luke had Mark’s gospel to hand when they wrote their gospels. Much of Mark is reproduced in their gospels, but they also added their own material and ‘corrected’ Mark in other passages. Here you see the editing process in action embedded in the New Testament.

This is not even to embark on the obvious mythological nature of the some of the stories and the many scientific errors found in the Bible.

Finally, on top of all these problems is the important point that the motivation of the gospel writers is suspect. The gospels, letters and other books of the Bible were not written primarily to accurately record facts; the bible was surely written as a means of religious instruction and to advance a particular religious line. That is analogous to propaganda. The motivation of those writing propaganda is of course suspect.

So, we are forced to the clear conclusion that the Bible books are not of any value as evidence of anything other than the state of mind of the people who wrote them.

Other forms of evidence

Expert, scientific and opinion evidence

Opinion evidence is not generally allowed in courts of law except when it comes from experts whose credentials and experience is such as to mean their expert opinion is reliable and helpful to a court.

Forensic evidence is an example of scientific evidence.

Photographs and CCTV

These can be very useful and helpful direct evidence. For example, dashcam evidence handed to the police at the scene of a road traffic accident. The source and authenticity of such evidence needs to be checked, as we know it can be tampered with and changed.

Computer generated evidence

Special rules apply to this category of evidence, not discussed here.

Bad evidence

The scriptures are not good evidence of what they purport to record for all the reasons set out above.

Documents are therefore often unreliable, and academics spend much time analysing ancient texts to try to identify their earliest form. A famous example is the ‘testimonium flavianum’ passage about Jesus found to have been inserted into Flavius Josephus’ History. Scholars think the forger was probably the ‘church father’ Eusebius. Eusebius’ apparent motivation was to advance belief in Christianity by inserting a passage in a history written in the same century as Jesus’ alleged life to create evidence of Jesus’ existence he, Eusebius, was sure of, and which he clearly felt should have been included in Josephus’s History of the period.

The Standard Islamic Narrative (SIN), is another example of traditions based on bad evidence when it comes to the origins of Islam. This is because the traditions (hadith) about Islam’s origins were written at least 100 years and up to 300 years after the events they purported to describe and were clearly the product either multiple hearsay or deliberate forgery, or both. Bukhari was a principal collector of these traditions, and he himself was aware of the problem because he rejected over 95% of the hadith he collected as unreliable or forgeries. Bukhari’s methodology in accepting the few he did accept is itself flawed.

Bad oral evidence

The case of ‘Our Lady of Fatima’ (aka the Virgin Mary) can be cited. Three schoolgirls claimed she would appear and perform miracles on 13th October 1917 at Fatima, Portugal.

Large crowds gathered to witness this event; they didn’t see the Virgin Mary, but they reported seeing the Sun move in the sky, perform zig-zags and emit multi-coloured lights. However, the remaining population of the world at the time did not see any such phenomena. This is thought to have been a case of mass hysteria.

Some medical conditions such as dementia and some medications for Parkinson’s disease are known to produce delusions at times expressed in religiosity in sufferers.

Another example of bad evidence commonly adduced is personal testimony. ‘I have a personal relationship with Jesus; I have met Jesus personally’. This is actual primary evidence, not hearsay. But the problem here is the usual one of personal gullibility and readiness to self-delude. Personal testimony of experiences which cannot be checked objectively is not good evidence; Such experiences are anecdotal and subjective evidence which is not high-quality evidence; little weight can be given to them.

This is where the problems of evidence meet the challenge of mental ill health. My observations of psychotic illness is that psychotic thoughts are often expressed in religious language and imagery, and that it is at times hard to distinguish the boundary between self-delusion and psychosis. Patients tell me they are Jesus, or that the angel Gabriel spoke to them, or that they have seen Jesus, Jesus talks to them, or that they have Jesus in their heart. Which are examples of religious devotion and which examples of psychosis?

‘Look at the Trees’ we are often urged as evidence of a creator god. This is more bad evidence. The natural world we see is evidence of … just the natural world. Perhaps we can infer the fact that the natural world has evolved from earlier states to the point where we experience it now. It is not in itself evidence of how it came about originally and certainly not evidence of a creator god. The fact that scientists cannot yet fully explain the origins of the universe does not automatically mean that a god did it.

What is good evidence?

Historians and Courts of Law look for credible evidence that is contemporaneous with the events they describe, which has not been changed or distorted, authored by known reliable persons who credibly witnessed or recorded recent facts or events they had personal knowledge of. Such evidence should not be inconsistent with our common sense understanding of the world. Even with this high-quality evidence mistakes and errors, including distortions in memory, can creep in.

Examples of good evidence are coins and inscriptions. Coins, which have lain undisturbed in the ground for centuries, will not have been tampered with; they record the facts stated on the coin accurately. This usually means the name of the ruler who issued the coins and often includes an image, symbol or claim that records what the ruler felt was important state propaganda to place on his coinage. Our coins show the Queen and the initials F D, which mean ‘Defender of the Faith’, an example of state propaganda (well past its use by date in the UK case).

Coins issued by the Arab empire of the 7th century after their extensive conquests from the 630s onwards in the Middle East, Iran and North Africa do not mention Mohammed before the end of that century. This fact runs counter to the SIN which implies that Mohammed was as famous as Mao Ze Dong and his little red book, while he still lived, and that he inspired the conquests made in that century.

Similarly, inscriptions may have remained undisturbed since the time they were carved and can reveal important information.

A good example is that there were no inscriptions that mentioned the prophet Mohammed at all until the 8th century in the areas where, according to the SIN, Islam held sway from the middle of the 7th century.

Tutankhamun’s tomb lay undisturbed for thousands of years and has yielded up much knowledge of the period he lived in, when interpreted by experts.

Another good bundle of evidence on the origins of Islam is the findings of Dan Gibson on Qiblas. Dan Gibson published his findings in 2011 (Quranic Geography) and 2017 (Early Islamic Qiblas) and also has a website.

Qiblas are the niche in a Mosque wall which shows the faithful which way they must position themselves to face Mecca during prayer. In Sura 2 verse 144, Mohammed changed the direction of prayer to Mecca for his followers. This change was effected after Mohammed emigrated to Medina (622) according to the SIN and before he died (632). The verse does not specify what direction prayers were offered before (though it is thought it may have been Jerusalem). However, Dan Gibson examined all the outstanding early mosques and found that all mosques built in the 7th century were built with their prayer direction facing Petra in Jordan, not Mecca. Here the evidence is of high quality: measurements taken which demonstrate the direction of prayer in the surviving buildings.

Dan Gibson is of course also an expert; he personally examined most of the mosques in question and he has set out his findings, including images and measurements. His expert interpretation of them is in his books and on his website, so that other scholars can check them. None have been shown to be incorrect so far.

Other scholars like Tom Holland in his famous book ‘Shadow of the Sword’ have made similar findings. He, for instance, included in his book a photograph of the ruins of a mosque in Sinai which had two quiblas, reflecting the change of direction. The Mosque was built well after 632 and in a place inconsistent with the change of direction of the qibla mentioned in the Quran. The photograph is evidence therefore that the change of the qibla direction took place much later than the SIN alleges as Dan Gibson’s case makes clear.

These findings and facts, based on good quality evidence, have led academics to doubt that Mohammed was the leader and preacher the SIN alleges him to have been, or that he came from Mecca at all. Indeed, his very existence is further put into doubt by this and other parallel quality evidence.

Weighing evidence and the quality of evidence

Every piece of evidence that is produced in support of any contention or faith claim needs to be examined, checked, and questioned. Its nature, quality and credibility needs determining, and the motivation of the witnesses needs to be considered, that is, it needs to be weighed.

The quality of the evidence refers to how good or bad the evidence is, while weighing the evidence is about deciding how much weight or credibility to give a witness or a piece of evidence. The weight of evidence is also used to refer to the quantity of good evidence received by a court on one or another side of a case.

The credibility of a witness may be enhanced by their reputation or standing, impartiality or presentation. On the other hand, it might be damaged by a bad reputation, the apprehension of bias or a shifty presentation.

Burden of providing evidence

This is sometimes referred to as the ‘burden of proof’. It is about who has the task of demonstrating the truth of a contention. Usually, the task of providing supportive evidence lies on the person who advances the contention and wants to persuade us to accept it, for example, the complainant in a court case. Such a person also has the task of countering objections to the evidence they produce.

This is the beauty of atheism which is a suspension of belief pending credible evidence of a god being adduced. But some of us want to go further and argue that on the balance of probabilities there are no gods. If we do that, we then take on the burden of demonstrating this argument with evidence and reasons.

Technically the word ‘proof’ is right only for mathematics and pure logic, where things can be proved absolutely. Elsewhere in science and philosophy it about convincing people, with good evidence, that the contention is probably true

Standards of proof

Three standards of proof are commonly used in courts of law. These are:

(a) the Criminal standard: the guilt of the defendant must be demonstrated to a high standard beyond reasonable doubt. The jury has essentially to be sure of the guilt of the defendant to convict him or her;

(b) the Civil standard: here the plaintiffs or complainants must prove their case on a balance of probabilities: the judge must find their case more probable than that of the defendant or respondent, and

(c) the Asylum standard where the danger to the asylum seeker must be demonstrated to be reasonably likely. This is lower than the civil standard.

It’s useful to bear these three standards in mind when debating theists.

All this information is second nature to lawyers for whom evidence is a key part of legal disputes, but it is important, too, when considering the claims that religious folk often make.

Philosophical arguments versus evidence

Finally, another distinction to bear in mind is the difference between evidence which supports a case or claim and philosophical arguments which purport to prove a claim without necessarily producing actual evidence, but which rely on (alleged) well established facts, basic propositions, and logic to advance a claim. Theists use all these methods in their forlorn efforts to prove their hidden god.


So far theists (and any god who thought we ought to be told about him/her/it) have failed to produce any evidence good enough to pass these quality and credibility tests.

Disclaimer: The views and opinions expressed in this article are those of the individual author(s) and do not necessarily reflect the official policy or position of Atheism UK.

Guy Otten

AUK Council member, member of organising team of Northern Atheists, vice chair of Greater Manchester Humanists and humanist chaplain at Meadowbrook psychiatric unit in Salford. Retired lawyer

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