Logical Fallacy #23: Tu quoque – appeal to hypocrisy

t turns out I missed #19, so all the numbers are out by one after that. Fixed now… (and the previous posts too!).

Tu Quoque is Latin for “you too” or “you also”. There are three flavours to this logical fallacy. The appeal to the common error in both sides of the discussion to excuse a mistake, the appeal to justify ones one errors based on a faulty perception of the others perceived mistakes and the discrediting of another’s failure to act consistently to their position.

The Pot Calling the Kettle Black

This is tantamount to a child in the playground excusing their bad behaviour with “X was doing it too!” Regardless of who else makes the error, it was still bad behaviour.

In the instance that a member of a discussion is caught using faulty logic or poor evidence, the perpetrator can either plead guilty, or may attempt to justify the error by citing the accuser of making the same or a similar error. This is a specific ad hominem attack attempting to shift the focus away from ones own mistakes to target the mistakes of another. In one flavour of this, the other may have indeed been mistaken, and in the other flavour, they are not. Either way, the fallacy is the same. Instead of addressing the noted error, the defendant diverts attention to some other error, whether real or not. The solution to this as someone who is called out on an error is to address the error. If the person receiving this logical fallacy, keep the focus on the error noted first, then address the accusation afterwards.

Dismissing the the Position

In this form of the logical fallacy, the position is ignored because of a self referential error in the arguments. This is a special case of the Fallacy Fallacy in that the fallacious argument becomes the focus instead of the position, which is dismissed. This can be best demonstrated in the following example:

Person A makes criticism C.

Person A is also guilty of C.

Therefore, C is dismissed.

Person 1: Drinking is bad for your health

Person 2: But your drinking!

In this case, the premise is that drinking is bad for ones health, which is dismissed by the second person because the arguer is currently drinking. Just because someone is guilty of participating in the activity or idea that is described does not make the activity or idea wrong. I can equally say that bashing my head against a wall is bad for your head whilst bashing my head against a wall. That doesn’t mean my head is not damaged by bashing my head against the wall.


Pot Kettle Black


Logical Fallacy #22: Moving the Goalposts / Shifting Sands

Originally from the British phrase where a goal post in a foot ball based sport is moved to advantage one side and disadvantage the other side, this logical fallacy denotes the situation where in the process of making an argument, the goal is shifted to make that argument either easier or harder. The fallacy resides in the moving of the goal whilst the process is taking place, rather than defining the goal first, then following the arguments to reach the target – either to support it or discredit it.

You may recall in the animated movie Robin Hood, by Walt Disney Productions, where Robin Hood (the fox) is disguised as a bird and attempting to shoot some targets in a competition to win a kiss from Maid Marianne (if not, go back and watch the movie – it’s awesome). His opponent, the sherrif of Nottingham,  shoots and the target jumps up and gets in the way of the arrow, making a bulls eye. This shifted goal post allowed an less competent archer to get a successful conclusion. In this example, the person moving the target is incapacitated so that Robin can shoot with skill alone, however if the person had not been incapacitated, they could have shifted the goal out of the way of the successful shot, creating a miss.

As a logical fallacy, the target can be moved closer for a poorly constructed experiment or argument to succeed where it shouldn’t (such as for the sherrif of Nottingham), or the target can be moved further away, to make a normally successful experiment or argument fail. This tactic is often used by proponents of psuedoscience, allowing their science to seem legitimate by using close goal posts, that is poor criteria, but then creating overly strict and stringent criteria for legitimate science to make it look faulty. Properly applied science uses the same criteria for all rather than shifting the rules.

An example from the “Supplement Industry” of this is defining their product as a diet supplement rather than a medicine, even though they make very medicine like claims [http://archinte.jamanetwork.com/article.aspx?articleid=647749]. The advertising targets legitimate medication as having nasty side effects and being full of chemicals, while the supplement itself does not have the advertised ingredient (1/3 in the USA), contain contaminants (1/5 in the USA) and no one really knows what the side effects are of the supplement, because there is no requirement to test them (according to the FDA in the USA) [http://theness.com/neurologicablog/index.php/whats-in-your-herbal-supplement]. By comparing the two as if they followed the same criteria yet the goal posts are shifted because medication must meet certain criteria such as testing, field trials, tracking, random checks etc, while supplements require none so can claim whatever they like without the requirement or burden of proof.

Robin Hood - Moving Target

Logical Fallacy #21: The Fallacy Fallacy

This logical fallacy focuses on the dismissing of outcomes due to a poorly constructed, or ignorant presentation, of the evidence or logic to support the outcome. Frequently this fallacy is mistaken for using a logical fallacy incorrectly or too rigorously, but it has more to do with throwing out the baby with the bathwater. The baby (the result) is still correct and useful, even if it is surrounded by dirty water (poor evidence and or poor logic and or not being an expert in the topic). It is important to recognise the outcome despite these factors.

I may perform a series of poorly conceived experiments to provide evidence of the strength of gravity. I may even get an accurate result despite the poor construction of my experiments. The correct result should not be dismissed just because of my poor experiments. Instead my experiment should be dismissed because of my poor experiment and the support of the accurate result should be negated. The Earth’s gravity is 9.8 m/s^2 at the surface, regardless of how poorly I experimented to get it. My poor experiment could also have ended up with 5 m/s^2 at the Earth’s surface, which is wrong and can be dismissed, or the experiment may have shown that I only get 9.8 m/s^2 if I stand on my left foot (the left foot part can be dismissed). If this experiment was the only one testing the Earth’s gravity, then the accurate result of 9.8 m/s^2 can be questioned because it is in isolation – so the 9.8 or the 5 have equal weighting. Experiments on Earth’s gravity are not uncommon though, so it can be quickly identified that 9.8 m/s^2 is accurate despite the poor experiment. The Logical Fallacy Fallacy comes in when I attempt to say that clearly Earth’s gravity is not 9.8 m/s^2 due to this poor experiment, despite the mountains of other experiments that actually demonstrate this is accurate.

Similarly to the poor experiment version, I may attempt to use logic to demonstrate that the sky is blue. The current leader of this country is an idiot, therefore the sky is blue in the daytime on a clear day. In this case, the logical fallacy used here is  a non-sequitur, attempting to link the idiocy of the current countries leader to the colour of the sky. Whether the countries leader is an idiot or not, or if the leadership were to change to someone else or not, or if there were not leadership in the country has absolutely no bearing on the colour of the sky. Yet the sky on a clear day is blue. Dismissing this as false because the supportive premise was faulty is not accurate and is the second example of a Logical Fallacy Fallacy.

I am not an expert on climate science. Nor am I an expert on biology, geology and a host of other sciences used to determine the current theory of Global Warming as part of Climate Change. I have a slightly above average laymans knowledge of this field, enough to know that the threat is real and that we should act. I can generally spot bogus anti-climate-change claims. Not being able to spell out the specific mechanisms and evidence supporting the conclusion of the vast majority of the worlds experts on this topic does not mean that they are wrong, it merely means that I am not an expert. This form of the Logical Fallacy Fallacy is again attempting to dump the baby (the mountains of evidence supporting global warming) because of the dirty water (my lack of specific expertise). It is a common tactic of the non-believer to find someone who is not an expert and dismiss the findings of the experts because the non-expert cannot adequately explain to them the science behind the evidence and conclusion.


Logical Fallacy Fallacy