Critical Thinking: More Logical Fallacies

In a previous post, we looked at the Ten Commandments of Logic, that laid out the most popular logical fallacies.  In this post we’ll go over some of the other common fallacious arguments that one is likely to encounter in almost any debate.

Just to recap,  a logical fallacy is an error in reasoning.  This differs from a factual error, which is simply being wrong about the facts.  To be more specific, a fallacy is an “argument” in which the premises given for the conclusion do not provide the needed degree of support.

Off we go…

“No True Scotsman”

Also referred to as the “No True Christian” argument, it is an informal fallacy; an ad hoc attempt to retain an un-reasoned assertion. When faced with a counterexample to a universal claim (“no Scotsman would do such a thing”), rather than denying the counterexample or rejecting the original claim, this fallacy modifies the subject of the assertion to exclude the specific case or others like it by rhetoric, without reference to any specific objective rule.  Put more simply, this fallacy occurs when either A) someone changes the definition of a word to make a claim true by default or B) a term is defined biasedly to allow easier use of the first form.  Instead of acknowledging that some members of a group have undesirable characteristics, the fallacy tries to redefine the group to exclude them.  Example:

Person A:  “Christians have waged just as much violence over the centuries as Muslims have – the Crusades, Inquisitions, Witch trials, etc.”                                                                                                                                               Person B:  “The people who did those things weren’t true Christians, because a true Christian would do that.”

Appeal to Authority

This is an argument from the fact that a person judged to be an “expert” or authority affirms a proposition to the claim that the proposition is true.  This can be a fallacy for two reasons: first, even a legitimate authority speaking on his area of expertise may affirm a falsehood, so no testimony of any authority is guaranteed to be true.  Second, the authority cited either (a) is not an authority, or (b) is not an authority on the subject on which he is being cited.

Whenever an authority is used, the following assessments must be made:

  • Does the person have sufficient expertise in the subject matter in question?
  • Is the claim being made by the person within his/her area(s) of expertise?
  • Is there is an adequate degree of agreement among the other experts in the subject in question?
  • Does the person in question have reason to be significantly biased?
  • Is the area of expertise a legitimate area or discipline?
  • Is the authority in question identified?

Slippery Slope

Closely related to a false dilemma, the slippery slope fallacy falsely assume that one thing must lead to another. This argument begins by suggesting that if we do one thing then that will lead to another, and before we know it we’ll be doing something that we don’t want to do. They conclude that we, therefore, shouldn’t do the first thing.  Examples:

Claim:  “If we allow gay people to get married, then that will open the door for people wanting to marry their pets or their relatives!”

Claim:  “If the government starts imposing stricter gun laws, before you know it, all guns will be banned!”

The problem with these arguments is that it is possible to do the first thing that they mention without going on to do the other things –  there is no reason to believe that one event must inevitably follow from another without an argument for such a claim.  This is especially clear in cases in which there is a significant number of steps or gradations between one event and another.

Appeal to Consequences of a Belief

In it’s much simpler terms – “wishful thinking”, an appeal to consequences is an attempt to motivate belief with an appeal either to the good consequences of believing or the bad consequences of disbelieving.  Some good examples of this can be found in the reasons people give for believing in God:

Claim:  “I acknowledge that I have no argument for the existence of God. However, I have a great desire for God to exist and for there to be an afterlife. Therefore I accept that God exists.”

Claim:  “If God did not exist, then all basis for morality would be lost and the world would be a horrible place!”

This line of “reasoning” is fallacious because the consequences of a belief have no bearing on whether the belief is true or false.

It is important to note that the consequences in question are the consequences that stem from the belief.  It is important to distinguish between a rational reason to believe (RRB) (evidence) and a prudential reason to believe (PRB) (motivation).   A RRB is evidence that objectively and logically supports the claim.   A PRB is a reason to accept the belief because of some external factor (such as fear, a threat, or a benefit or harm that may stem from the belief) that is relevant to what a person values but is not relevant to the truth or falsity of the claim.

Red Herring

Simply put, this is when the arguer diverts the attention by changing the subject.  The basic idea is to “win” an argument by leading attention away from the argument and to another topic, but merely changing the topic of discussion doesn’t count as an argument against a claim.  Example:

Claim:  “Evolution is not a very good explanation for human life. Anyway, I am pretty offended that anyone would suggest that I came from a monkey.”

Appeal to Emotions

Closely related to Appeal to Popularity fallacy, this fallacy is committed when someone manipulates peoples’ emotions in order to get them to accept a claim as being true.  More formally, this sort of “reasoning” involves the substitution of strong emotions in place of evidence for a claim.

Appeals to emotion are very common in politics and religion, and it serves as the basis for a large portion of modern advertising.  Peoples’ emotions often carry much more force than their reason. Logical argumentation is often difficult and time consuming and it rarely has the power to spurn people to action.  It is the power of this fallacy that explains its great popularity and wide usage.


There are many more logical fallacies out there, but this (plus the Top 10 covered earlier) covers the majority of the ones you’ll come across.  If you are interested in a more complete list, you can check out the links below.

These last few posts have been more informational then my typical posts, but I wanted to write them as much for my own understanding as for others.  It will also be good to have them on here as reference in future posts.  Now that I have them out of the way we can “return now to our regular scheduled programming” as they say.  I can get back to speaking from the heart and ruffling a few feathers!  Thanks for reading.


NOTE:  Most of the descriptions found in this post were taken from other websites, namely the Nizkor Project, and Logical

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