Fallacy 101

Below is a list of logical fallacies frequently used by the woo brigade. I’ll add to these as I encounter them.

If you’re not sure what a logical fallacy is, or what logic is, try these useful links:

Ad Hominem – attacking the person, not the argument. E.g. “James Randi is just a stage magician, what does he know about scientific proof?”.

Ad ignorantum – argument from ignorance, or misplaced burden of proof. Arguing that something is true because the other side cannot prove it isn’t true. E.g. “We cannot know that god doesn’t exist, therefore he exists”

Appeal to Emotion – aka argument by emotive language, this is the use of emotionally charged words or phrases used to provoke a knee-jerk reaction from the opponent. These are usually also red herrings, in that they do not actually have anything to do with the argument at hand, but are thrown in for the specific purpose of evoking an emotional response. E.g. “Dr. Kent Hovind is denied bail and is sitting in a jail cell, while a child molestor is granted bail and is sitting at home.” The statement would have almost zero impact if one had contrasted him to a dirty accountant, or an importer of pirated dvds. The use of ‘child molestor’ in this statement is purely for emotive impact, and is otherwise irrelevant.

Argument from Authority – arguing that because someone who is a perceived authority supports an argument, it is therefore true. This is irrelevant – an argument should stand on its own merits, not on those of the person doing the arguing. E.g. “Einstein believed in god, therefore god must exist” or “Kary Mullis won a nobel prize and he believes in astrology, therefore there must be something to astrology”

Argument from Final Consequences – aka teleological arguments. Arguments based on the reversal of cause and effect, arguing that something is caused by the ultimate effect it has. E.g. “Life has no meaning without the existence of God, therefore God exists”

Argument from Personal Incredulity – arguing that because you personally cannot explain or understand something, it must therefore not be true. E.g. “I don’t believe we’re related to apes, therefore evolution can’t be true” or “quantum mechanics doesn’t make any sense to me, therefore it must be made up by scientists and can’t possibly reflect reality”

Argument from Popularity – arguing that because most people believe something to be true, it must be true. E.g. “every newspaper has a horoscope section, therefore astrology must work or it wouldn’t be so popular”

Argument from Probability – arguing that because the chances of X being true are small, X is not true. Generally based on a poor understanding of probability E.g. “the chances of life occuring on earth are so small that it must have required divine intervention”. This argument makes two mistakes – the first is the fallacy that small probability means zero probability, and the second is simply not taking into account that over sufficient time, even events with a low probability are likely to occur.

Association does not imply causation – just because two events occur together, does not imply that one causes the other. This is only cogent if a causative link can actually be demonstrated. E.g. “Children are diagnosed with autism at the same age as they receive MMR vaccines, therefore MMR vaccines cause autism”

Begging the Question – when the premises of an argument contain their conclusion. E.g. “I have a strong personal sense of the presence of God, therefore God exists” – this argument assumes that your feeling is caused by the existence of God, so your argument already assumes your conclusion. This is not proof of your conclusion.

Currently unexplained does not imply unexplainable – Just because we don’t have an explanation for something now, does not imply that it is inherently unexplainable. E.g. “Scientists don’t currently know what caused the first instance of self-replicating life on earth, therefore no scientific explanation will ever be found, leaving only god as an explanation”

False Dichotomy – arbitrarily assuming that there are only two solutions, and that disproving one is proof of the other. E.g. Intelligent Design advocates attempting to disprove evolution as a proof of intelligent design, ignore the possibility of additional theories.

Guilt by Association – assuming a claim to be false merely because the claimant is personally disliked by the arguer, or associating the claimant’s shortcomings with the claim. E.g. “Hitler was an atheist, therefore atheism is evil”

Humpty Dumpty – so named for the scene in Alice in Wonderland where Humpty Dumpty argues that he can use a word to mean whatever he wishes it to mean. Ignores the fact that the meaning of a word must be agreed on by both parties before an argument can be based on it. E.g. “Science says that energy is conserved, therefore the soul must live on after death” – this claimant is not using ‘energy’ in the same sense that scientists use it, therefore the argument is not cogent.

Inconsistency – applying criteria or rules inconsistently in order to win an argument. E.g. Christians often argue that we cannot know the motives of god, yet they also claim to know that he sent his son to die for our sins.

No True Scotsman – the name of this argumentative fallacy was coined by Anthony Flew in his 1975 book Thinking About Thinking. The example he gives goes as follows: Argument: No Scotsman puts sugar on his porridge. Reply: But my uncle Angus likes sugar with his porridge. Rebuttal: Ah yes, but no true Scotsman puts sugar on his porridge. It involves the continual redefinition of an argument in response to contrary evidence, is a form of shifting the goalposts, and does not necessarily need to explicitly take the form of ‘no true x’. E.g. in response to a claim that one used to believe in God but no longer does: “I’m curious as to why you stopped believing in God, if in fact you really believed at all.” The suggestion is that regardless of the reason, if you stopped believing, you must not have been a true believer in the first place.

Poisoning the well – a sort of pre-emptive ad hominem attack, whereby someone tries to discredit another’s point by biasing the audience against them before they’ve made the point. “Oh, here comes Richard Dawkins, don’t listen to what he says, he just hates god and wants all religious people to go to hell by turning against god.”

Post hoc – fully “post-hoc ergo propter hoc”, literally “after this, therefore because of this”. Confusing sequence with cause. Assuming that because B followed after A, B was caused by A. E.g. “I prayed to god that I would win the lotto, and then I won the lotto. My prayers were answered”

Red Herring – the act of introducing a subject into an argument that in fact has no real relevance to the argument, and has merely been introduced to steer the subject away from the topic at hand. “So what if homeopathic medicines don’t work? Western medicine kills people!”

Reductio ad absurdum – actually a valid logical argument that is misused in the extreme. When correctly used, reductio ad absurdum arguments state that if assuming an argument’s premise to be true, it results in an obviously false conclusion, then the premise must in fact be false. Generally misused in the form of purposefully reducing an argument to absurdity in order to make the premise seem to be false. E.g. “skeptics are skeptical about the existance of X, so they should be skeptical about the existance of everything they haven’t personally experienced” – the implication of course being that it’s ridiculous to be skeptical about everything and therefore skepticism is inherently wrong.

Relativist Fallacy – stating that a claim may be true for others but is not true for you. E.g. “The evidence points to UFO abductions being merely delusions or false memory, and that is true for some people but i know i was really abducted” or “All other religions are foolishly worshipping the wrong god, but my religion worships the right one”

Shifting the Goalposts – moving the criteria for acceptance of an argument continually out of range of evidence, in order to ensure that regardless of the quality of evidence, the criteria for acceptance is never met. E.g. “Okay, I know i said that if you showed me proof of speciation i’d accept evolution, but what i really want is proof of…”

Slippery Slope – arguing that A, via the processes of B through Y, will lead to Z. Z is undesirable, therefore A is undesirable. This argument is not always a fallacy, but requires significant proof that A does in fact lead to Z. E.g. “If we let IVF clinics give excess embryos to stem cell research, eventually they’ll keep manufacturing more and more excess embryos until we just have stem cell embryo factories disguised as IVF clinics”

Straw Man – creating a charicature of an argument, because the charicature is more easy to destroy than the actual argument. E.g. “Evolution is a completely random process, and the likelihood of something as complex as humans arising from a completely random process is so small as to be impossible” – straw man, because evolution is not at all a totally random process, but is in fact dependent on non-random selection.

Special Pleading – also known as ad-hoc reasoning. Adding a qualifier in an ad hoc and unsupported manner in order to make an argument appear to be valid. E.g. “Astrology failed that test because science is not a good test of astrology” or “ESP doesn’t work in the presence of skeptics”

Tautology – an argument that uses circular reasoning of the form A=B therefore A=B, or A=A e.g. “psychic healing can heal wounds without medical intervention or the need for surgery” – this statement is tautological, because psychic healing is defined as such. The definition of a thing does not constitute its proof.

Tu quoque – literally “you too”, also ad hominem tu quoque. Attempting to make the false true by implying that the opponent holds the same false claim, therefore must believe it to be true. Alternately, just arguments of the form ‘so what if my proof is poor, so is yours’. E.g. “I believe in god, scientists believe in the scientific method! Therefore they must agree that belief is okay” or “So what if my proof of homeopathy is weak? Your proof of western medicine is weak”

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