5: Logical Fallacies
- Page ID
- 306941
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Early on in the exploration of reasonableness we made a point of acknowledging basic human fallibility. Inquiry is not a linear path from absolute truth to absolute truth. Inquiry is a more typically a meandering path with frequent back tracking as we learn from or mistakes. Our conclusions, even when they support a healthy degree of confidence, remain always provisional. New evidence or argument may reveal previously unrecognized mistakes. Of course, learning from our mistakes does require that being able to recognize them. Many of the mistakes in reasoning we humans are prone to are well known. These are fallacies. A fallacy is just a mistake in reasoning. Assuming we’ve developed a decent understanding of what good reasoning looks like over the prior chapters, we should now be in a position to examine some common fallacies and understand why they are mistakes.
A fallacious argument fails to support its conclusion. This is all that we can conclude when we find that an argument contains a fallacy. Finding an argument to be fallacious does not in itself provide a reason for rejecting its conclusion. There might be other good arguments for that conclusion or good arguments against it. The value in fallacy spotting is that it gets tempting but bad arguments out of the way and thereby helps us get a clearer view on issues. Reasonable people won’t want to believe false things for bad reasons or true things for bad reasons. Bad reasons distort our understanding of the world, often in ways that indulge biases or prejudices, as we’ll see in a few examples below.
I will only discuss a choice selection of fallacies here. A full course in critical thinking would introduce you to many more and include lots of practice at identifying them, first in text book exercises, then “in the wild.”
- 5.1: Ad hominem
- This page discusses the ad hominem fallacy, which shifts the focus from an argument's substance to attacking the individual presenting it. This tactic hinders meaningful dialogue and leads to polarized discussions. It provides an example involving a car salesman, where dismissing valid arguments based on the seller's motives results in missed valuable information. The page concludes that the validity of an argument is independent of the character or intentions of its presenter.
- 5.2: False Dichotomy
- This page discusses dichotomies, highlighting the choice between two mutually exclusive options, like the debate on extraterrestrial life. It distinguishes true dichotomies from situations with multiple options, such as meal choices. The page addresses the fallacy of false dichotomy, exemplified by George W. Bush's post-9/11 remarks on Iraq, which oversimplified public opinion by presenting only two stances: support for the war or alignment with terrorists.
- 5.3: Straw Man
- This page explores the straw man fallacy, particularly in climate change debates where critics mischaracterize advocates as socialists. It points out that such oversimplifications divert focus from the essential need for collaboration between government and businesses in addressing climate issues. The text stresses the importance of effective action over succumbing to misleading criticisms, which often spread more readily than constructive counterarguments.
- 5.4: Hasty generalization
- This page discusses how the human brain's tendency to recognize patterns can result in hasty conclusions, particularly influenced by fear and anxiety. It highlights the dangers of these generalizations, linking them to injustices like racial prejudice and antisemitism, exemplified by propaganda leading to the Holocaust. The page also points out ongoing issues of racial injustice, especially against Black Americans, underscoring the risks of relying on flawed reasoning and manipulated evidence.
- 5.5: Spurious Correlation
- This page examines the fallacy of inferring causation from correlation, specifically addressing crime rates among different races. It argues that higher crime rates among Black Americans are better explained by systemic issues like economic inequality and racial bias instead of innate criminality. The text emphasizes that lack of opportunities, such as unemployment, is a more significant causal factor for crime, suggesting that the crime-race correlation is misleading.
- 5.6: Confirmation bias
- This page highlights the significance of recognizing fallacies, particularly focusing on confirmation bias, which promotes favoritism towards evidence that aligns with existing beliefs, weakening critical thinking. It notes that confirmation bias can encompass various fallacies and hinder credibility even with strong support. To counteract this bias, the text stresses the importance of enhancing critical thinking skills, such as evaluating arguments and identifying fallacies.