Types of Logical Fallacies

Fallacies are mistaken beliefs based on unsound arguments. They derive from reasoning that is logically incorrect, thus undermining an argument's validity.

Fallacies are difficult to classify, due to their variety in application and structure. In the broadest sense possible, fallacies can be divided into two types: formal fallacies and informal fallacies.

Let's take a look at the variations that exist within these categories.

Formal Fallacies

Formal (or deductive) fallacies occur when the conclusion doesn't follow the premise. These are often referred to as non-sequiturs, or conclusions that have nothing to do with initial claims. In formal fallacies, the pattern of reasoning seems logical but is always wrong. A deductive argument often follows the pattern: (1) All dogs have legs. (2) Tiny is a dog. Therefore: (3) Tiny has legs.

Appeal to Probability - This is a statement that takes something for granted because it is probable or possible.

  • I see a dark cloud on the horizon. Dark clouds mean rain. It's going to rain here today.

Bad Reasons Fallacy - Also known as Argumentum ad Logicam, in this type of fallacy, the conclusion is assumed to be bad because the arguments are bad.

  • Her new boyfriend drives an old car. He must be poor. She should break up with him.

Masked Man Fallacy - Also known as the Intentional Fallacy it involves a substitution of parties. If the two things that are interchanged are identical, then the argument is assumed to be valid.

  • Jeremy's private investigator reported that a man with a beard was having dinner with his wife. Jeremy's best friend, Ronnie, has a beard. Therefore, Ronnie is having an affair with Jeremy's wife.

Non Sequitur - A fallacy wherein someone asserts a conclusion that does not follow from the propositions.

  • All Dubliners are from Ireland. Ronan is not a Dubliner, therefore, he is not Irish.

Informal Fallacies

Informal (or inductive) fallacies abound. Not only are we more likely to come across them than formal fallacies, their variations are endless. While formal fallacies are identified through an examination of the statement or claim, informal fallacies are identified through supporting evidence.

In these instances, the statement or claim is not supported with adequate reasons for acceptance. A strong inductive argument follows this pattern: (1) The sun has not exploded for all its existence. Therefore: (2) The sun will not explode tomorrow.

Subcategories of Informal Fallacies

There are so many varieties of informal fallacies they can be broken down into subcategories. Let's examine some of those subcategories.

Fallacies of Presumption

Presumption of truth without evidence can also cause fallacious reasoning. Examples of these fallacies include:

Complex Question Fallacy - This involves questionable assumptions.

  • "Are you going to admit that you're wrong?" Answering yes proves you're wrong. Answering no implies you accept you are wrong, but won't admit it. This question presumes guilt either way.

Hasty Generalization Fallacy - This is based upon only one abnormal situation. It is the reverse of a sweeping generalization fallacy.

  • Hitler was a vegetarian. Therefore, I don't trust any vegetarians.

Post Hoc, Ergo Propter Hoc - This (meaning "after this, therefore because of this") is based upon an assumption of cause and effect, A happened, then B happened, so A must have caused B.

  • I saw a magpie and then I crashed my car. Magpies are bad luck.

Cum Hoc, Ergo Propter Hoc - This fallacy (meaning "with this, therefore because of this") is when the person making the argument connects two events that happen simultaneously and assumes that one caused the other.

  • Hospitals are full of sick people. Therefore hospitals make people sick.

Slippery Slope Fallacy - This falsely assumes the consequences of actions.

  • If we let your brother stay, we'll have to let your whole family stay.

Sweeping Generalization Fallacy - This includes too broad of an application of a premise.

  • Running is a good way to keep fit, so everyone should run a mile every day.

Tu Quoque Fallacy - This applies the concept of "Look who's talking" and is used to turn criticism against the other person.

  • "You shouldn't have that second piece of cake. It's so fattening"
"Didn't you eat an entire tub of ice cream yesterday?"

Appeal to Ignorance - Or Arguing from Ignorance, these fallacies abound in everyday conversation, advertising, politics, and history. This fallacy argues that a proposition is true because it has not yet been proven false.

  • During his Communism investigations Joe McCarthy presented a case saying, "I do not have much information on this except the general statement of the agency…that there is nothing in the files to disprove his Communist connections." His argument was that, because there was no evidence against a Communist connection, that person must be working with the Communists. (Source: Senator Joe McCarthy, Richard H. Rovere, Methuen, 1960).

Circular Argument - Also referred to as Circulus in Probando, this fallacy is when an argument takes its proof from a factor within the argument itself, rather than from an external one.

  • I believe that Frosted Flakes are great because it says so on the Frosted Flakes packaging.

False Dilemma- Sometimes referred to as Bifurcation, this type of fallacy occurs when someone presents their argument in such a way that there are only two possible options.

  • If you don't vote for this candidate, you must be a Communist.

Fallacies of Ambiguity

A fallacy can also be caused by a lack of clarity or by a misunderstanding of the words. Examples of these fallacies include:

Accent Fallacies - These are based on the stress or emphasis of a word or word parts being unclear

  • Depending on which word is stressed in the sentence "I didn't take the test yesterday", has several meanings, such as someone else took the test or I took it another day.

Equivocation Fallacies - These occur when words are used multiple times with different meanings.

  • You have faith in science, and I have faith in God.

Straw Man Fallacies - These include misrepresentations to make an argument look weak.

  • First senator: The nation is in debt and we should not add to the defense budget.
    Second senator: I cannot believe you want to leave the nation defenseless!

Fallacies of Relevance

These fallacies attempt to persuade people with irrelevant information, appealing to emotions rather than logic. Examples of these fallacies include:

Appeal to Authority - also referred to as Argumentum ad Verecundia (argument from modesty). In this case, rather than focusing on the merits of an argument, the arguer will try to attach their argument to a person of authority in order to give credence to their argument.

  • Well, Isaac Newton believed in alchemy, do you think you know more than Isaac Newton?

Appeal to Popular Opinion - This type of appeal is when someone claims that an idea or belief is true simply because it is what most people believe.

  • Lots of people bought this album, so it must be good.

Attacking the Person - Also known as ad Hominem, this is quite a common occurrence in debates and refers to a person who substitutes a rebuttal with a personal insult.

  • Don't listen to Eddie's arguments on education. He didn't even finish high school.

Bandwagon Fallacy - This contains arguments that are only appealing because of current trends and growing popularity.

  • More people are turning to meditation and mindfulness to help them cope with the stress of modern-day living. Therefore meditation can make us all calmer.

Gambler's Fallacy - This assumes that short-term deviations will correct themselves.

  • This coin has landed heads-up nine times in a row. So it will probably land tails-up next time it is tossed.

Genetic Fallacy - This involves acceptance or rejection of concepts based on their source, not their merit.

  • My best friend says you're a liar, so I'm not going to talk to you.

Red Herring Fallacy - This uses irrelevant information or other techniques to distract from the argument at hand.

  • You bring up gay marriage and claim that I'm against it but isn't it just as important to talk about the issue of homeless veterans. Did you know that I volunteer at a local shelter?

Weak Analogy - These fallacies employ analogies between things that are not really alike.

  • Cars kill people just like guns, but if you're not going to ban the sale of cars you can't ban the sale of guns.

Using Fallacies

In argumentation or debate, bad reason fallacies are quite common. How often do you hear people compare two unrelated things while making judgments? We sometimes make character judgments about others based upon their material possessions or the friends they keep when one tends to have nothing to do with the other.

When making a case in a research paper or essay, it's easy to fall into the trappings of an appeal to authority fallacy. Examples, statistics, and testimony are all important measures of supporting evidence in an academic paper. We just need to make sure that we're drawing proper conclusions from the authority figure to the case we're developing.

In advertising, appeal to authority fallacies abound. Celebrity endorsements are popular for a reason. If we decide we like the lifestyle of a certain celebrity, then we are likely to purchase the sports drink, jewelry, or organic food they are pitching. This is an easy fallacy to fall prey to. Perhaps if we purchase this item being advertised, we might be more like our beloved celebrity. It might be best, however, to purchase a product based upon its proven benefits, not the celebrity being paid to pitch it.

If you watched any of the 2017 presidential election debates, you would've seen countless attacking the person fallacies. Political opponents spend hundreds of thousands of campaign dollars to undermine their opponent's legitimacy and make them look unqualified.

Think Logically

As we can see, there are many different types of fallacies. Informal fallacies are particularly complex because layers of subcategories exist within them. Now that you know what some of the most prevalent fallacies look like, we hope you'll be able to identify these lapses in logic right away! Take a look at Examples of Fallacies to dive even deeper into these multi-faceted waters.

Types of Logical FallaciesTypes of Logical Fallacies

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