Logical Fallacies

Here’s some quick summaries of logic and logical fallacies:


Deductive Logic
Bolstered by Rene Descartes
– Example: All ravens are black.  That is a raven.  Therefore, it is black.
– Process in which a conclusion is reached by a series of premises. 
– Logic Example: P = Q, Q = R, Thus, P = R

Inductive Logic
Bolstered by Francis Bacon
– Example 1: This raven is black and that raven is black.  Therefore, all ravens are black.
– Example 2: This swan is white.  Therefore, all swans are white.
– Note: It only takes one black swan to prove it wrong.
– Process of generalizing premises or a sample to the population of the relevant context. 

➡ Logical Fallacies:

+ This is the fallacy where a statement is made that does not follow from the premises or conclusions.  It is usually intuitive to note it as nonsense.
– Example 1: We found his fingerprints on the gun.  Therefore, guinea pigs are evil.
– Example 2: If all boys like chocolate and chocolate is given for free, then the sun revolves around the earth.

Illicit Appeal to Authority

+ Although we often rely on experts in fields for professional opinions, we somtimes entirely rely an arguments credibility on a professionals opinion.

+ What kind of people should not be relied upon?
– It is a fallacy to rely on those that lack of expertise of the relevant issue, who have no expertise in the relveant issue, and people talking about matters that are known to be problematic (ie. issues that are of subjective nature or inconclusive conclusions)

+ When is it okay?
– When other and independent experts agree with the claim that they are making (ie. gravity is real), and it must be possible for you yourself to check the claim by some systematic observation (ie. drop a cup). In other words, you should always be able to examine the evidence that the experts used to establish the relevant point.

Ad populum; Argument from popularity

+ Sometimes we believe something just because everyone else does, or many others hold a similar belief.  However, if it is a popular belief, then it should be all the more easier to verify its cogency. It is unnecessary and a fallacy to simply accept a belief because other people do.
– Example 1: There is good reason to believe in God; people in every culture, at all times, believed in a God. Therefore, I believe in God.
– Example 2: Everyone smokes, therefore, you should smoke to.

Ad Hominem Argument (against the person, to the man)

+ This is the attempt to make a criticism of the opposition by directly attacking the person purporting arguments. This is a fallacy because the legitimate criticism should be made to the proposed argument, not the person giving the argument. Even evil people can say completely cogent things
– Example 1: Freud’s theories should never be considered in any field.  After all, he did do drugs and was obsessed with sex.
– Example 2: 
Circular Reasoning

+ It is a fallacy to presuppose the truth of your conclusion in your premises. If you are going to assume your conclusion is true before trying to prove it, you are using circular reasoning. 
– Example: There must be a God, since there bible and quan both say there is and the bible and quran were inspired by God.

Begging the question

+ Similar to circular reasoning. When the reasoning for the conlcusion depends on accepting the truh of the conclusion. 

Slippery Slope

+ This is a type of argument in which one makes the claim that one event will inevitably lead to greater other consequences. Often, this further consequences have no relevance or the person does not show a chain of causation. It is usually used as a scare tactic in order to convince others to not follow a certain opposition
– Example 1: If gay marriage is legalized, polygamy will be legalized, and even worse, and soon people will be marrying their relatives and pet animals, thus, same-sex marriage will lead to social chaos.
– Example 2: Marijuana is a “gateway drug”. Marijuana leads to the usage of cocaine.

Straw man

+ The straw man tactic is to take the opposition and set the arguments in a way that is easier to attack or misrepresents their claims. 
– Example: Very popular edited videos of Richard Dawkins by creationists to try and prove him wrong:

Fallacy of Equivocation

+ This fallacy is commited when a key word in an argument is used in two or more sense and the premises seem to support the conclusion. However, this is because the sense of the defined words are not distinguished. It will seem to make sense but only if the words are not defined separately.
– Example 1: Everything evil is black. Everything good is white. Thus, black people are evil.
– Example 2: Theism is better than nothing. Nothing is better than Theism. Thus, theism is better than nothing.

Red Herring

+ Not necessarily a fallacy but an attempt to divert attention away from the real issue. 
– Example 1: Richard Dawkins “What If You’re Wrong?”

– Although his answer is thorough, it does not technically answer the question. However, if he were to add the presumed “I don’t know” or “I would go to hell” then it would be perfectly fine. Creationists often use this as an example to show how Dawkins is wrong – which is a thoroughly false assumption because he explains his answer thorooughly afterwards. 
– Example 2: “I believe in abortion” “Really? Well, the doctor there that does abortions is also a wife beater!” Although it may be true that the doctor beats his wife, it has nothing to do with abortion.

Tu quoque


+ This is the attempt to divert attention of vices to the opposition.  It stands for, “You too!” and is usually when someone is trying to show that you are just as faulty for the pointed flaw as they are.  While it may be true that you are at fault for something, it is a fallacy to ignore the point in favour of attacking the other.  Truthfully, this is usually just an attempt to save-face rather than admit being wrong.


Confusing Correlation with Causation


+ There is a plethora of evidence out there involving correlations and they are often used to imply a causation of a factor.  So, with more X we have more Y.  However, that does not mean that X causes Y, it only indicates a relationship or coincidence.


Post-hoc ergo propter hoc


+ “After this, therefore because of this” follows correlations perfectly because it is the exact fallacy that is being used.  It is also common for someone to think that because a certain variable simply happened before another, that it must have caused it.
– Example 1: I bought a stock in apple then terrorists crashed into the WTC.  Therefore, buying stocks causes terrorist attacks.
– Example 2: Helen moved into my house and then I noticed cockroaches in my basement.  Therefore, Helen causes cockroaches to appear.


False Analogy


+ Often in arguments, we use analogies to draw similarities between concepts to relay a point.  However, there is the fallacy of using an analogy between two things which have no relevant variables.
– Example 1: Gun control is like birth control.


Examples of debates using fallacies


Media examples chock full of fallacies, can you find them..?

What do you think..?

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