How we know what to rely upon

Lots of people seem to be very confused about the nature of evidence and the meanings of terms such as ‘theory’, ‘hypothesis’, ‘science’ and ‘nonsense’. So I’ve put together a little table that I hope will be helpful. It might clear up a few misunderstandings.

For example the phrase ‘only a theory’ doesn’t mean it’s not reliable. In fact, in the case of very strong theories such as the theories of evolution or gravity it’s as close to fact as cautious, scientific convention will allow. Creationists beware – you have no idea how silly you appear when you use that particular phrase to try to knock down Darwinian evolution.

I’ve made some amendments to the table below. This is because some people have challenged the ranking of the examples I used in the original. Since the point of this post is to outline the hierarchy itself I’m quite happy to use different illustrations. I may yet make further amendments in the light of scientific evidence for reincarnation which I have been promised and am hoping will actually materialise. Incidentally that’s the main advantage of scientific thinking methods over ‘Just so’ stories like creationism. Scientific thinking involves accepting when the evidence demonstrates that we have been wrong and changing our minds accordingly. That’s why scientific understanding moves on whereas creationism (for example) is essentially making the same, tired arguments that the Rev. William Paley first came up with 200 years ago.

Anyway – I hope this table helps clear up some issues for the hard-of-understanding among us.

If your browser only displays half the table just double click it to see the whole thing.

Evidence hierarchy 2

Fallacies 18: Appeal to authority

In the last ‘Fallacies’ entry we considered the appeal to popularity. In this entry we’ll look at a similar tactic known as the appeal to authority. This is a common argument used to shortcut any analysis of the issues and jump straight to the conclusion:
“Professor such-and-such thinks this is right so who are we to argue?”

There is some merit in this line of argument, especially when discussing complex issues about which most people know very little. We need to rely upon the judgement and opinions of experts simply because nobody has the time to study everything in enough depth to make informed decisions on all the topics that come up in modern society.

But if we don’t know enough to make our own decisions then we need some way to judge which expert does. This is no easy task.

It’s an old question that was first discussed (to the best of my knowledge) by Plato, an ancient Greek philosopher who covered it in his ‘Discourses’. Plato came to a rather unsatisfactory conclusion. He argued that the only way to judge the value of expert opinion is to become an expert yourself.

As we have seen this isn’t really an option. But if we want to make sense of the world we have to try because let’s face it – even experts can be fallible.

We have several basic problems here…

Expert in the right field

An expert in one field isn’t necessarily an expert in another. Indeed – the time and effort required to become an expert in any field means that it’s very unlikely that most people will be able to do it in more than one area of study. But it’s not enough to have a Ph.D. – you need to have the right Ph.D.

For example it is not uncommon for creationists to argue that some (admittedly not all that many) leading scientists deny evolution. But you’d be hard pushed to find an evolutionary biologist (or even a general biologist) to take their claims seriously. This was the crux of the problem with the 2005 school curriculum trial in Dover, Pennsylvania.

Although some members of the community and the school board wanted ‘Intelligent Design’ (the new incarnation of creationism) to be pushed on to the vulnerable minds of children in science classes, those who understood the issues (the teachers) refused. The case went to Court and (of course) the teachers won.

Is your expert authority skilled in the right field?

Is your expert authority skilled in the right field?

It’s not enough to cite an expert – it must be an expert in the appropriate area of study because nobody knows everything.

This was the problem with Bjorn Lomborg’s controversial work on climate change (The Skeptical Environmentalist, 2001 and Cool it, 2007). Lomborg is not a climate scientist, he has a Ph.D. in political science. The overwhelming majority of actual climatologists (those who understand climate science) reject his work out of hand and it’s not hard for even a layman to understand why.

His arguments contradict themselves (he can’t even make up his mind whether or not global warming is a good thing) and the evidence he uses to uphold one argument is conveniently ignored when he tries to make a different point without the merest hint of explanation.

None the less climate change deniers and right wing politicians regularly cite his work as an ‘appeal to authority’. This would be like asking someone with a Ph.D. in theology to recommend treatments for psychiatric patients, a ridiculous situation indeed. It isn’t reasonable to expect someone with no knowledge of the relevant field to be taken seriously when they make recommendations. None the less this is precisely what Archbishop John Sentamu did when he suggested in the UK’s House of Lords that exorcism should be available to psychiatric patients on the National Health Service.

Archbishop Jphn Sentamu thinks people with mental health problems should be subjected to (NHS funded) exorcism

Archbishop Jphn Sentamu thinks people with mental health problems should be subjected to (NHS funded) exorcism

Authority in the organisation

There are other types of authority to be wary of though. There’s the authority that comes from organisational structure – the boss.

As we all know people rise through the ranks in organisations for a variety of reasons and they’re not always the best person for the promotion. Managers are promoted because someone owes them a favour, because nobody else wants the job, because they have a good relationship with powerful outside funders or supporters or sometimes even because they know stuff.

Often though they are just in the right place at the right time. That’s not exactly a qualification for the status of expert. I’m sure I’m not the only person who has worked for incompetent managers and spent significant amounts of my time sorting out the messes they created.

The Peter Principle is the phenomenon of promoting people to the level of their own incompetence. The fact that John is a good technician doesn’t mean he will be able to manage other technicians or run a departmental budget. But he gets promoted (because of his technical ability) into a job that requires a completely different skillset – and John just can’t cut it.

But he doesn’t get sacked or demoted back to his former position. He just stays where he is. He’ll never climb any higher because he’s not good at his lower management job so he just stays there – perhaps for decades – making poor decisions and holding back his department’s progress. That’s the Peter principle at work. You’d be a fool to trust John’s judgement about anything to do with management. He’d be great at answering technical questions though. That’s his real area of expertise.

Experts are fallible

Even true experts are fallible. That’s why Alfred Russel Wallace (co-discoverer of the theory of evolution) was suckered by spiritism and spent much of his life vociferously supporting fraudulent mediums. He was good at what he did but he was far from perfect – just like the rest of us.

Whenever we try to assess the credibility of experts we come up against these sorts of problems and it’s genuinely difficult to know who to trust. It’s almost impossible to make that decision with absolute certainty. But there are some questions we can ask ourselves that may help:

Is this expert skilled in this particular area?
What do the majority of similairly trained experts think?
What does the evidence say?
How often has this person been right/wrong in the past?
If they’ve been wrong before have they been prepared to admit it?
Is this person ideologically driven?
Is this person financially driven to say this stuff?
Are there any other forms of bias you are aware of?
Does the expert use real data as evidence or just rely on stories and anecdote (you can make any point you like in a story)?
If you follow them and they are wrong – will there be a cost?
If you don’t follow them and they are right – will there be a cost?
What research could you do to check out their assumptions?

You see there’s much more to being right than merely being an expert or a boss.

The appeal to authority has merit – in fact it would be impossible to function in the modern world without trusting someone but it’s always a good idea to think carefully about which authority you choose to follow.


We have now reached the end of this blog series as originally planned. However I’ve enjoyed writing it so much I’m sure I’ll be adding to the ‘Fallacies’ blog category as time progresses.

About the ‘Fallacies’ series

The ‘Fallacies’ project was built up from a series of instalments that first appeared online during the summer of 2012. It is republished as part of a larger set of changes intended to rationalise the contents of several different blogs into just 2. The other remaining blog focuses mainly upon social care and mental health related issues. It can be found at

Fallacies 17: The appeal to popularity

Appeal to popularity
It’s truly remarkable how many different tactics people will use to persuade us of their point of view. One of the most common is the ‘appeal to popularity’ in which we are encouraged to agree simply because a significant number of other people do. It’s an appeal to herd mentality in which reason is seen as less important than populism. This is the argument that would have us believe the Nazis were correct simply because so many people attended the Nuremberg Rally.

Of course that doesn’t mean that popular opinion is always wrong – far from it. But when popular opinion is reasonable it is because, coincidentally it matches the available evidence, not merely because it is popular.

Columbus disagreed with the majority view

Columbus disagreed with the majority view

An interesting aspect of this argument is that it relies solely upon a statistical analysis, an opinion poll if you will, and such statistical perspectives are notoriously misleading. Different populations give different results. Different cultural groups often have predictable opinions and different views are prevalent at different periods in history.

Unless we believe that modern society is infallible we need to be open to the possibility that popular opinion today may be wrong just as it was when most people believed that:

The earth is flat;
The earth is the centre of the universe;
Iron ships can never float;
Erupting volcanoes, failing harvests, infertility and disabilities are the judgements of the Gods.

And then there is the problem of sampling. For example I know a number of people who proudly insist that most people in the world believe in a God or Gods. They’re not usually quite so keen to report that most people the world over do not believe in their particular deity of choice. Nor do they generally like to acknowledge that (with the curious exception of the United States), the more advanced the nation the smaller the percentage of believers.

You see the question you ask about statistics of any kind can easily be used to manipulate the results to make whatever case you like. But that really just makes the very idea of the ‘appeal to popularity’ both meaningless and obsolete.

So what if most people in rural Kenya believe that unprotected sex with a virgin will cure AIDS? Most people who have studied the disease understand how tragic and dangerous such a very popular misconception really is. It results in the widespread rape of young girls who often go on to develop AIDS themselves as a direct consequence. So which statistic matters most?

The reality is that every major advancement in human understanding involved an individual or minority group disagreeing with the majority. This is how we develop as a society.

Will you follow the herd or will you think for yourself?

Will you follow the herd or will you think for yourself?

If the ‘appeal to popularity’ argument had held sway Eddison would never have developed electric lighting, Darwin would never have developed his theory of evolution and Columbus wouldn’t have rediscovered the Americas several centuries after Leif Erikson’s forgotten expedition to ‘Vineland’ (modern Newfoundland).

Dismissing the minority view simply because it is the minority view stymies growth and prevents improvement. It’s far better to judge an idea on its merits than worry about the numbers of supporters it may have. Every good idea was outside the mainstream once upon a time.

Instead of counting heads, ask what the evidence is for new ideas and beliefs. Who cares what the herd thinks? Unless, of course, you’re a sheep.

About the ‘Fallacies’ series

The ‘Fallacies’ project was built up from a series of instalments that first appeared online during the summer of 2012. It is republished as part of a larger set of changes intended to rationalise the contents of several different blogs into just 2. The other remaining blog focuses mainly upon social care and mental health related issues. It can be found at

Fallacies 16: The Star Trek fallacy (The argument from internal circularity)

wpid-2012-09-01-18-36-52-2057740132.jpeg“Klingons are OK as a species but I wouldn’t want to make one angry.”
“Come again.”
“I said I wouldn’t want to cross a Klingon.”
“It’s a good job they’re not real then.”
“What do you mean? Of course Klingons are real.”
“Oh, come on. What evidence do you have of the existence of Klingons?”
“They’re in the book.”
“What book?”
“The Star Trek annual 1979. My mother bought me it when I was a boy. Klingons are in there. It’s written in black and white.”
“That’s not evidence. It’s just a collection of stories.”
“Well it’s evidence enough for me. I believe in Star Trek & Klingons. I also believe in the Ferengi and the Borg Collective. If it wasn’t true it wouldn’t be in the book.”

Nobody in their right mind would be convinced about the existence of Klingons because of such a ridiculous argument. We need more than words on a page – we need some sort of evidence too. And anyway everybody knows that it’s fiction. The Star Trek stories are fictional metaphors. They’re just parables intended to illustrate aspects of contemporary morality. That’s why the moral messages have developed to reflect changing social values from the 1st episodes in the 1960s to the latest episodes some 40 odd years later.

And nobody would seriously try to justify casual sexism or slavery by referring to the early episodes of Star Trek in which Captain Kirk supported both. Times have changed and a 40 year old TV script neither proves nor justifies anything.

Incidentally, an old book from the bronze age is no better qualified to justify sexism, homophobia, neoliberalism, creationism, racism, murder, eugenics, disablism, capital punishment, anti-abortion legislation, holy war, inequalities of wealth or ethnic cleansing. Nor does the existence of that book prove the existence of a God anymore than a Star Trek annual from 1979 can prove the existence of Mr. Spock.

Believe what you like but if you want to influence society in ways that affect the rest of us you’ll need more than just an argument from internal circularity to get my support.

About the ‘Fallacies’ series

The ‘Fallacies’ project was built up from a series of instalments that first appeared online during the summer of 2012. It is republished as part of a larger set of changes intended to rationalise the contents of several different blogs into just 2. The other remaining blog focuses mainly upon social care and mental health related issues. It can be found at

Fallacies 15: Correlation = causation

One of the first symptoms of the bubonic plague that caused so much devastation throughout Europe was the sensation of a sweet smell. This was not caused by an actual scent in the air but rather by physical processes related to the illness.

But, because the smell always accompanied the plague (was correlated with it) people assumed that it was the cause. They also likened the sores that appeared on the bodies of victims to flowers because they bore a superficial similarity to them. This is why physicians adopted large beak-like masks which they filled with sweet scented flowers. It was an attempt to ‘fight fire with fire’ and drive away the scent of the illness with sweet scents of their own devising. It also prompted people to carry sweet smelling flowers around in their pockets hence the rhyme:

A ring, a ring of roses,

A pocket full of posies,

Atishoo, atishoo,

We all fall down.

Of course, with the benefits of modern scientific understanding we know that flowers have nothing to do with plague and that carrying roses around in your pocket or donning a beak filled with scent won’t prevent it. It was a pointless exercises but understandable in the circumstances. After all – people didn’t know what else to try. So they relied upon the only correlation they could think of and based their remedies upon the desperate hope that correlation somehow would equal causation. Unfortunately for the many who died, it didn’t – and it still doesn’t.

That’s all very interesting but it’s hardly relevant today. We know that illness isn’t driven off by sweet smelling flowers and the follies of the past don’t really apply to the modern world. Or at least we’d like to think they don’t. In reality the correlation – causation fallacy still persists even though modern examples of it may be different.

thumbnailCA3H80ASA relatively recent illustration of this was the widespread assertion (which appeared to originate with research conducted by the Chinese government) that prolonged internet use caused depression. This conclusion was reached because the researchers had discovered a correlation between depression and time spent on the worldwide web.

For the moment we can leave aside the possible motivation of the Chinese government in claiming that internet use is unhealthy. That may be a factor to consider when evaluating this research but it’s not the focus here. I’m going to assume that the correlation exists just as the researchers claimed.

Based upon this correlation the researchers concluded that the internet causes depression but could there be another explanation?

We know that one of the symptoms of depression is withdrawal.
We know that people who withdraw tend to find things to do that don’t really involve face to face contact with others.
We know that it is very easy to find relatively passive distractions on the internet.
We know that in mild depression people don’t tend to sit around and do nothing – they simply find passive things to do instead.

We can see then that we have a typical ‘chicken and egg’ quandary here. Does the internet use cause depression or does the depression prompt increasing use of the internet as an alternative to real world contact?

Of course it’s also true that increasing isolation can deepen depression but that still doesn’t mean that the internet is the cause. The same thing would probably happen if the depressed person sat and drew pictures or watched TV all day long. The internet may just be incidental.

To be fair I have no way of knowing whether or not the internet is significant. It might be but there isn’t nearly enough information to make a judgement. We have only a correlation and correlation isn’t causation.

We could just as easily claim that since there is a correlation between short-sightedness and wearing glasses that glasses cause short-sightedness. Perhaps using crutches is a clear cause of broken legs too.

Correlation isn’t causation. This is obvious in the two examples above (short-sightedness and broken legs) because we know enough to understand the cause and effect. But when we don’t understand that relationship in advance it’s very dangerous to draw any conclusions. Particularly if all we have is evidence of correlation.

Fallacies 13: Ad hominem

Literally ‘Ad hominem’ means ‘to the man’ although most people today would translate it as ‘about the man’. In truth the meaning probably isn’t significantly different in context but there seems little point in inviting criticism in the light of recent events. So – to be clear – in this blog post the translation we’ll use is ‘about the man’.

The ‘Ad hominem argument’ is a very common tactic that people use when they have no real contribution to make. Instead of commenting upon the issues at hand they will attack the other person as though highlighting what they perceive to be a character flaw or an unappealing personality trait will somehow negate everything that the opposing speaker has said.

Of course it doesn’t take much thought to realise just how silly that approach really is. For example:

The notion that Isaac Newton (reputedly) was less than sociable didn’t take anything away from his genius or from the validity of his insights into the physical universe;
The fact that Enid Blyton had an intense dislike of children didn’t prevent her from writing stories that delighted children everywhere;
The fact that Napoleon Bonaparte was prepared to slaughter men in huge numbers to achieve his goals does not mean that his ideas about universal education or a codified legal system were wrong.

Just as the idea of a single cause can be fallacious, so is the idea that people can be defined by a single character trait or behaviour. The idea that a person can never be correct in anything they say or do is even more ludicrous and yet this is the very assumption that underlies the ad hominem argument.

There may well be a case for questioning a person’s motives based upon their past behaviour. There may well be a case for characterising the person (in context) as a way to help us understand a situation. Indeed I did exactly that myself recently when writing to my ‘troll’ But that wasn’t the only argument I put forward.

People characterise each other on a very regular basis. They question each others’ motives. Sometimes they even get their assumptions about other peoples’ motives right. But that’s not an argument in itself. It may provide context but that’s about all.

An ad hominem argument alone is not worth listening to because without addressing the issues themselves it has no substance. People are complex and everyone is flawed to a greater or lesser extent but that doesn’t mean that our human flaws prevent us from having anything valid to say.

If the only argument that the other person presents is ‘ad hominem’ then it’s generally a good idea to ask yourself why they haven’t said anything more. Why haven’t they addressed the real issue instead of indulging in cheap insults or ad hominem attacks? The answer may well be because there genuinely isn’t a valid argument that they could have made.

About the ‘Fallacies’ series

The ‘Fallacies’ project was built up from a series of instalments that first appeared online during the summer of 2012. It is republished as part of a larger set of changes intended to rationalise the contents of several different blogs into just 2. The other remaining blog focuses mainly upon social care and mental health related issues. It can be found at

Fallacies 12: The false dichotomy

Anders Breivik

Anders Breivik

The false dichotomy argument (AKA Black & white argument, false dilemma argument, fallacy of exhaustive hypotheses) is a favourite of a range of manipulators from quacks and politicians to clerics and snake-oil salesmen. It is a tactic used to convince the other person that there are only two possibilities when in reality there are more. For example…

The English Defence League claims to defend England from what it regards as the ‘Islamification’ of the Western world. You may have heard that argument before. It’s the one Anders Breivik used to justify his terrorist attacks in Oslo last year.

The argument is depressingly simplistic, allowing for only two possibilities….

‘The Muslims’ will take over the world
We will stop ‘the Muslims’ from taking over the world

It’s not hard to see that there are many, many more possibilities than this. Other possibilities include…

People can learn to live harmoniously together.
Many parts of UK are peacefully integrated.
‘The Muslims’ is no more an homogenous group than ‘The Christians’ is. There are ‘good and bad’ in both religions.
The extremist antics of the EDL and other far-right neoNazi organisations is a bigger threat by far to our society than the presence of people whose creed or colour differs from the stereotypical ‘Aryan Christian’ ideal.
All people, regardless of race, colour or creed have equal rights.

And yet, by creating a false dichotomy this divisive group of neoNazis have managed to convince themselves that standing around in car parks and attacking anyone who looks a bit foreign somehow constitutes defending the nation.

An equally silly false dichotomy involves the political nonsense that led David Cameron and Theresa May to inform us that the UK’s only options were:

Scrap the Human Rights Act
Watch the collapse of the British economy.

Dale McAlpine preaching

Dale McAlpine preaching

It’s true that the British economy isn’t doing particularly well right now but there’s much more to the argument than workers’ rights and a legal system that protects minimum wages and opposes unfair dismissal. Reducing tax for the highest earners, destroying the public sector and using tax payers money to boost private profits might have something to do with it too – not to mention the global financial crisis.

One of my least favourite false dichotomies came from a West Cumbrian, Christian street preacher who kindly informed my autistic, teenage stepson that he had only two options…

Convert to fundamentalist Christianity
Burn in Hell for all eternity

As you may imagine I was sure to point out a range of options to that preacher when I saw him in the street some time later.
And yet the narrow focus of the false dichotomy continues to influence people and can actually sound quite convincing if we accept their assessment of the situation at face value.

So I’ll set up a little dichotomous argument of my own. You can judge for yourself whether or not you consider the dichotomy to be a false one……

When you are presented with only two options ask yourself if
there may be more things to consider

Remain vulnerable to these manipulators and their superficial assessments of reality

About the ‘Fallacies’ series

The ‘Fallacies’ project was built up from a series of instalments that first appeared online during the summer of 2012. It is republished as part of a larger set of changes intended to rationalise the contents of several different blogs into just 2. The other remaining blog focuses mainly upon social care and mental health related issues. It can be found at


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