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.