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CRITICAL T HINKING – H ANDOUT 11 – ARGUMENTS BY ANALOGY
1. Analogies
To say that two things (or cases) are analogous is to say that they are comparable in some relevant respect. Many analogies are used to better explain a difficult, obscure, or abstract concept in terms of something that is easier to understand, less mysterious, and concrete. To illustrate,
“Mama always said life was like a box of chocolates. You never know what you're gonna get.” –Forest Gump
The idea is that life and chocolate are comparable in the respect that both involve making decisions in a state of uncertainty. For instance, consider a box of chocolates whose insides are filled with a variety of different flavors. Whenever you pick a chocolate, you are unsure whether it is filled with coconut, caramel, cherry, etc. You have to just take a bite and see what flavor it is. The uncertainty of picking chocolates is used to explain (make clearer) the uncertainty of life , e.g. when some choices you make seem one way on the surface but upon closer inspection turn out to be a different way. An analogy that simply uses one concept/thing to explain another is known as a figurative analogy. Their primary purpose is to create a conceptual linkage between two things that are similar in some respect, typically for the purpose of explaining a complicated concept in terms of a simpler concept. Argumentative analogies are arguments that employ analogies as premises. Typically, arguments by analogies contain three parts:
- The analogy (as a premise) which contends that two different cases ( A and B ) are analogous, i.e. they share some relevant feature x.
- A statement that says from case A , some proposition P follows.
- The conclusion that says since case A and case B are analogous, and P follows from A , then it also follows from B.
Here is the basic structure of an analogy:
Structure of a Argument by Analogy 1 (analogy) Case A is analogous to case B 2 (statement) Concerning A , P is true. 3 (conclusion) Therefore, concerning case B, P is true.
is analogous to Analogy Case A Case B (uncontroversial) (controversial)
Statement P is true Conclusion Thus, P is true
To put this somewhat differently:
Structure of a Argument by Analogy 1 (analogy) Case A is relevantly like case B 2 (statement) Concerning A , you think that P is true. 3 (conclusion) Therefore, concerning case B , you should also think that P is true.
To illustrate:
A Simple Argument by Analogy 1 (analogy) Water is analogous to wine. 2 (statement) If you carelessly step on a floor with water on it, you will slip. 3 (conclusion) If you carelessly step on a floor with wine on it, you will slip.
There are two major types of arguments by analogy: deductive arguments by analogy and inductive arguments by analogy.
2. Deductive Arguments by Analogy
A deductive argument by analogy is a deductively valid argument that contains an analogy as one of its premises. Earlier we said that an argument by analogy contains three components: (1) the analogy between two cases A and B, (2) a statement P follows in case A, and (3) the conclusion that P follows from case B. However, there are two key additions to this three part analysis. First, we said that arguments by analogy contain an analogy (as a premise) which contends that two different cases ( A and B ) are analogous, i.e. they share some relevant feature x. Many arguments by analogy, however, do not specify what specific relevant feature x that A and B share. That is, they do not specify exactly how A and B are analogous. Thus, in order to analyze arguments by analogy, we add a fourth feature (1a), which is an explanation of the analogy.
Structure of a Deductive Argument by Analogy 1 (analogy) Case A is analogous to case B 1a (explained) Typically Unstated: A and B share some specific relevant feature x 2 (statement) Concerning A , P is true. 3 (conclusion) Therefore, concerning case B, P is also true.
Second, in order for the argument by analogy to be deductive valid , we need a principle that makes it such that if the premises were true, the conclusion must be true. Without this principle, it would be possible for the premises to be true and conclusion false. For consider that it is possible for A and B to share a similar feature x, for P to be true in A, yet for P to be false in B.
Structure of a Deductive Argument by Analogy 1 (analogy) Dogs are analogous to cats 1a (explained) Both share feature x , where x = furriness. That is, both are furry. 2 (statement) Dogs bark. 3 (conclusion) Therefore, cats bark.
Example #2 of a Deductive Argument by Analogy, see pp.165- 168 1 (analogy) Humans eating animals (e.g. cows) is analogous to aliens eating humans. 1a (explained) The case of humans eating animals and aliens eating humans share a relevantly similar feature x, where x = using greater intelligence to justify inflicting pain (and raising them for food) on another being. 2 (statement) It is wrong for intelligent aliens to inflict pain on us by raising us for food. 2a (principle) 3 (conclusion) Therefore, it is wrong to inflict pain on animals just because we are more intelligent than they are.
Finally, we need to specify the principle that says every case where a more intelligent creature justifies inflicting pain (and raising them for food) on a less intelligent creature on the basis of having greater intelligence.
Example #2 of a Deductive Argument by Analogy, see pp.165- 168 1 (analogy) Humans eating animals (e.g. cows) is analogous to aliens eating humans. 1a (explained) The case of humans eating animals and aliens eating humans share a relevantly similar feature x, where x = using greater intelligence to justify inflicting pain (and raising them for food) on another being. 2 (statement) It is wrong for intelligent aliens to inflict pain on us by raising us for food. 2a (principle) Every case where a greater intelligence is used to justify inflicting pain on something is wrong.. 3 (conclusion) Therefore, it is wrong to inflict pain on animals just because we are more intelligent than they are.
The construction of the analogical argument is now complete. However, before turning to a discussion of how to criticize deductive arguments by analogy, it is helpful to see why arguments by analogy are so effective.
2.2. Why Use Arguments by Analogy?
Consider the structure of a deductive argument by analogy:
Full Structure of a Deductive Argument by Analogy 1 (analogy) Case A is analogous to case B 1a (explained) Typically Unstated: A and B share some specific relevant feature x 2 (statement) Concerning A , P is true. 2a (principle) Typically Unstated: For any case that has feature x , P is true. 3 (conclusion) Therefore, concerning case B, P is also true.
What an argument by analogy does is consider two different kinds of cases: an uncontroversial case A and a controversial case B. Next, it says that if you think about the uncontroversial case A , you find that you believe P (and you believe this on the basis of some principle). Finally, it says that if you the two cases are analogous, and you believe P in case A on the basis of some general principle, then you also ought to believe P about the controversial case B. Thus, what arguments by analogy do is forge a relationship between something controversial and
uncontroversial, then rely on what you already believe concerning uncontroversial matters (and why you believe it) in order to get you to believe something similar about a controversial matter.
Principle, for all x, P is true.
A & B share x Analogy Case A Case B (uncontroversial) (controversial)
Statement P is true Conclusion Thus, P is true
In sum, it aims to start from a foundation of common agreement and extend agreement to a controversial issue.
Controversial Case: Humans eating animals Uncontroversial Case: Aliens eating humans. Uncontroversial Statement: It is wrong for aliens to inflict pain on us by raising us for food Principle: Greater intelligence is not a justification for one being inflicting pain on another. Controversial Statement (Conclusion): It is wrong to inflict pain on animals by raising them for food because we are more intelligent than they are.
Classroom Activity : In a small group, create your own analogical argument and write it on the board. Be sure to fully develop the argument using the structure provided.
2.2 Two Ways to Criticize Deductive Arguments by Analogy
There are three ways to criticize deductive arguments by analogy.
- Criticize the Analogy (2a) by arguing that A is not analogous to B. That is, argue that A is not relevantly similar to B.
- Criticize the Statement (2) and the Principle (2a) by saying that the statement is false and that the principle is false.
- Accept the Statement (2) but reject the Principle (2a) by denying that A and B both imply the Principle (2a).
The first way to criticize deductive arguments by analogies is to reject the analogy upon which the argument is built.
- Reject the Analogy (1a), i.e. reject that A and B share some specific relevant feature x. In the case of the water/wine example, this would amount to saying that water and wine are not liquids. In the case of the human/alien example, this would amount to saying that
Let’s consider the following example:
Full Structure of a Deductive Argument by Analogy 1 (analogy) Alcohol prohibition is like marijuana prohibition 1a (explained) During alcohol prohibition there was organized crime in Chicago (which was funded by an illegal substance) and there is organized crime now in Mexico (which is funded by an illegal substance). 2 (statement) Legalization of alcohol eliminated organized crime in Chicago. 2a (principle) For any situation where a substance is illegal and there is organized crime, legalization of the substance that funds that organized crime will eliminate that crime. 3 (conclusion) Legalization of marijuana will eliminate organized crime in Mexico.^3
In the case of the above analogy, you might reject (1a) by arguing that there is not organized crime in Mexico funded by an illegal substance. In criticizing (2), you might reject that alcohol eliminated organized crime in Chicago. In the case of (2a), you could say that there is a reason for thinking that the legalization of alcohol eliminated crime in Chicago but it will not eliminate crime in Mexico, e.g. because the Mexican cartels have a much more economically diverse criminal organization.
Ex. pp.169: Ex.11-1 #1-
Full Structure of a Deductive Argument by Analogy 1 (analogy) 1a (explained) 2 (statement) 2a (principle) 3 (conclusion)
Criticism #1 : Reject the analogy (1a). Criticism #2 : Reject the statement (2). Criticism #3 : Reject the principle (2a).
Full Structure of a Deductive Argument by Analogy 1 (analogy) 1a (explained) 2 (statement) 2a (principle) 3 (conclusion)
Criticism #1 : Reject the analogy (1a). Criticism #2 : Reject the statement (2). Criticism #3 : Reject the principle (2a).
Full Structure of a Deductive Argument by Analogy 1 (analogy) 1a (explained)
(^3) For a specific example of this argument, see Stephen Colbert’s interview of Ethan Nadelmann (Episode #05059).
2 (statement) 2a (principle) 3 (conclusion)
Criticism #1 : Reject the analogy (1a). Criticism #2 : Reject the statement (2). Criticism #3 : Reject the principle (2a).
3. Inductive Arguments by Analogy
An inductive argument by analogy is an inductive argument (an argument that goes beyond the information in the premises by making a projection on the basis of them) that contains an analogy as one of its premises. As such, it is an argument where it is possible for the premises to be true and the conclusion false.
Full Structure of an Inductive Argument by Analogy 1 (analogy) Case A is analogous to (relevantly similar to) case B 1a (explained) Case A and Case B share the following similarities: x , y , and z. 2 (statement) In case B , P is true. 2a (principle) (^) If A and B are similar in some respects, then it is likely that they will hold in other respects. 3 (conclusion) Therefore, in case A , P will be (is likely to be) true.
For example,
Full Structure of an Inductive Argument by Analogy 1 (analogy) The Michael Phelps of 2012 is like the Michael Phelps of 2008. 1a (explained) Michael Phelps of 2008 and 2012 both are excellent swimmers, in the Olympics, and have been training very hard. 2 (statement) The Michael Phelps of 2008 won the gold medal in the 200m butterfly. 2a (principle) (^) If Michael Phelps of 2008 and 2012 are similar in being excellent swimmers, in being in the Olympics, and having trained very hard, then it is likely that they will hold in the further respect concerning winning gold in the 200m butterfly. 3 (conclusion) Therefore, the Michael Phelps of 2012 will win gold in the 200m butterfly.
An inductive argument by analogy can range in strength from very weak to very strong. There are two key features that determine the strength of an argument:
- The amount and variety of the features that A and B share.
- The relevance of the features shared between A and B with respect to the conclusion
If A and B are similar in many relevant ways, then you are likely to have a strong argument. However, if A and B are similar in only a few ways or if the similarities are not really relevant to the conclusion, then you are likely to have a weak argument. For example, suppose that Michael Phelps of 2012 is very different than the Michael Phelps of 2008, e.g. he was paralyzed, hated swimming, wasn’t training, etc., then the argument would be weaker. In addition, suppose that there was a great deal of overlap between Phelps of 2008 and Phelps of 2012 but they were
