Lecture Notes by Christopher Lay

Los Angeles Pierce College

Department of History, Philosophy, and Sociology

Mathew Van Cleave's 2016 Introduction to Logic and Critical Thinking

https://open.umn.edu/opentextbooks/BookDetail.aspx?bookId=457

Review for Chapter 4 "Informal fallacies"

"A fallacy is simply a mistake in reasoning."  

With "an informal fallacy ... we have to rely on our understanding of the meanings of the words or concepts involved ... ." 

Sub-§ 1 "Composition Fallacy"

"In the composition fallacy one argues that since each part of the whole has a certain feature, it follows that the whole has that same feature." 

The fallacy has this form: "Every part of X has the feature f. Therefore, the whole X has the feature f." 

Sub-§ 2 "Division Fallacy"

"Division Fallacy"

"The division fallacy ... argues that since the whole has some feature, each part must also have that feature."  

"Just because the whole [has a property], it doesn’t follow that each part of the [whole has the same properties]." 

Sub-§ 3 "Begging the Question"

In begging the question, "the premise is essentially the same claim as the conclusion." 

"[T]he premise is essentially saying the same thing as the conclusion."   

"Begging the question occurs when one (either explicitly or implicitly) assumes the truth of the conclusion in one or more of the premises." 

"But if the premise is the same claim as the conclusion, then it can’t possibly provide a reason for accepting the conclusion[.]"

Sub-§ 4 "False Dichotomy"

"A false dichotomy is simply a disjunction [that is, an either/or statement] that does not exhaust all of the possible options."

The problem with the fallacy of false dichotomy is that "the first premise presents two options as if they were the only two options, when in fact they aren’t, the first premise is false and the argument fails." 

Sub-§ 5 "Equivocation"

"[I]n the fallacy of equivocation [a] the word ... is used equivocally—that is, in two different senses." 

One word can be used in two different senses (for example, a figurative sense and a literal sense) in one and the same argument. 

"[T]he definition of the fallacy of equivocation refers to [the way in which] the same word is being used in two different senses (i.e., with two different meanings)." 

§ 2 "Slippery Slope Fallacies"

"Slippery slope fallacies depend on the concept of vagueness." 

"When a concept or claim is vague, it means that we don’t know precisely what claim is being made, or what the boundaries of the concept are."

"There are two fallacies related to vagueness: the causal slippery slope and the conceptual slippery slope."

Sub-§ 1 "Conceptual Slippery Slope Fallacy"

"[J]ust because we cannot draw a distinction between A and B, and we cannot draw a distinction between B and C, it doesn’t mean we cannot draw a distinction between A and C." 

Just because it can be difficult to distinguish between two small difference, "it doesn’t follow from this that there is no distinction to be drawn between" other differences. 

Sub-§ 2 "Causal Slippery Slope Fallacy"

"The causal slippery slope fallacy is committed when one event is said to lead to some other (usually disastrous) event via a chain of intermediary events," and "is committed when one assumes that just because each individual conditional statement is probable, the conditional that links the first event to the last event is also probable." 

"Even if we grant that each 'link' in the chain is individually probable, it doesn’t follow that the whole chain (or the conditional that links the first event to the last event) is probable." 

"[I]n a causal slippery slope fallacy, the link between each event is probabilistic. It is the fact that each link is probabilistic that accounts for the fallacy." 

§ 3 "Fallacies of Relevance"

"Fallacies of relevance can be compelling psychologically, but it is important to distinguish between rhetorical techniques that are psychologically compelling, on the one hand, and rationally compelling arguments, on the other.

"What makes something fallacy is that it fails to be rationally compelling, once we have carefully considered it." 

"That said, arguments that fail to be rationally compelling may still be psychologically or emotionally compelling." 

Sub-§ 1 "Ad Hominem"

"In an ad hominem fallacy, instead of responding to (or attacking) the argument a person has made, one attacks the person him or herself." 

"In short, one attacks the person making the argument rather than the argument itself."   

"[W]hen considering an argument that has been given, we don’t have to establish the arguer’s credibility because we can assess the argument they have given on its own merits." 

"The arguer’s personal life is irrelevant."

"Not every instance in which someone attacks a person’s character is an ad hominem fallacy." 

"[B]ringing up things about the witness’s past, [can be] relevant to establishing the witness’s credibility." 

Sub-§ 2 "Straw Man"

"The straw man fallacy misrepresents one’s opponent’s argument and is thus a kind of irrelevance."

In the straw man fallacy, one gives "a rationally compelling argument against" a position that is "much less plausible (and thus much easier to refute)" than the actual, target position. 

In the straw man fallacy, one argues against a straw version of the actual, target position. 

The target position is the actual position that one should confront, but when one instead confronts a different but related position, one has committed the straw man fallacy. 

In the straw man fallacy, one merely argues against "a position that 'looks like' the target position" (like the way a straw man looks like a real human), and not the actual, target position.

Sub-§ 3 "Tu Quoque"

"The tu quoque fallacy is a way of avoiding answering a criticism by bringing up a criticism of your opponent rather than answer the criticism." 

"Tu quoque, as [presented in this textbook], is fallacious when the criticism one raises is simply in order to avoid having to answer a difficult objection to one’s argument or view."   

Sub-§ 4 "Genetic Fallacy"

"The genetic fallacy occurs when one argues (or, more commonly, implies) that the origin of something (e.g., a theory, idea, policy, etc.) is a reason for rejecting (or accepting) it."  

The genetic fallacy is committed when one fails to recognize that "[t]he origin of an idea has nothing inherently to do with its truth or plausibility."   

"[I]deas must be assessed on their own merits and the origin of an idea is neither a merit nor demerit of the idea." 

Instead of dismissing something because of its origins, one should instead "explain what, exactly, is wrong with[, for example] the idea rather than simply assuming that there must be something wrong with it since it has a negative origin."

"Although genetic fallacies are most often committed when one associates an idea with a negative origin, it can also go the other way: one can imply that because the idea has a positive origin, the idea must be true or more plausible."   

Sub-§ 5 "Appeal to Consequences"

"[T]he appeal to consequences fallacy consists in the mistake of trying to assess the truth or reasonableness of an idea based on the (typically negative) consequences of accepting that idea." 

The appeal to consequences mistakenly accepts or rejects something because of what it leads to. 

"The consequences of some idea (good or bad) are irrelevant to the truth or reasonableness of that idea."

"[S]ometimes truth can have negative consequences and falsehoods can have positive consequences. This just goes to show that the consequences of an idea are irrelevant to the truth or reasonableness of an idea." 

Sub-§ 6 "Appeal to Authority"

According to our textbook: "In general, an appeal to authority fallacy occurs when someone takes what an individual says as evidence for some claim, when that individual has no particular expertise in the relevant domain (even if they do have expertise in some other, unrelated, domain)."  

According to me: an appeal to authority happens when one presents what someone with relevant authoritative knowledge would say about something without also including the reasoning that supports what such an authority would say about that thing. 

(Inasmuch, I am in agreement with Porter's (2002) The Voice of Reason: Fundamentals of Critical Thinking description of this fallacy: "the argument from authority (ipse dixit argument) ... [is a fallacy that is] committed whenever we argue for some point, not because it is well grounded in fact or logic but because of the authority of the person who presented it."

Granted, if someone has authoritative knowledge about something, the word of such an authority on a relevant matter should not be just dismissed.  Importantly though, the word of such an authority on a relevant matter should be presented with some kind of evidence other than their authority to support it. 

In addition to an appeal to someone's authoritative knowledge, support for their claims are warranted. 

(More from Porter's (2002) The Voice of Reason: Fundamentals of Critical Thinking description of this fallacy: "[A]n idea does not become true simply because an authority says so; the person must have good reason to say so. ... . If we accept people as authorities it is because we have confidence that they support their insights with good thinking and good evidence. ... .   Furthermore, the evidence should be publicly verifiable, whether in the form of reproducible experiments or rational reasons that anyone can consider."