Wednesday, May 20, 2015

Analogical Arguments

An analogical argument is the use of a comparison between two or more things which have some similarity and from this basis inferring that they share some other property. The central topic which is dealt with in the conclusion is often referred to as the primary subject and the thing to which the primary subject is compared to is called the analogue.

As described by Govier "An argument based on analogy begins by using one case (usually agreed on and relatively easy to understand) to illuminate or clarify another (usually less clear). It then seeks to justify a conclusion about the second case on the basis of considerations about the first. The grounds for drawing the conclusion are the relevant similarities between the cases, which show a commonality of structure."

The general form of an analogical argument is:

P1. A has properties p, q, r
P2. B has properties p, q, r
P3. A has property s
C. Therefore B has property s

For example:

P1. John's brother and parents smoked two packs of cigarettes a day and ate fatty foods.
P2. John smoked two packs of cigarettes a day and ate fatty foods.
P3. John's brother and parents all died prematurely of heart attacks.
C. Therefore, John will probably die prematurely of a heart attack.

The strength or weakness of an analogical argument depends upon a number of considerations:

Similarity - Verify that the properties proposed as being shared among the comparison group do indeed exist. As analogical arguments are rarely actually presented in the form above, it may even be necessary to first list just how it is assumed the comparison groups are similar. Here is a simple example. "John is like Mike. Mike is smart. Therefore John must be smart". In this example none of the assumed similarities between John and Mike have been presented. Before the argument can carry any weight these similarities must be listed and verified.

Relevance - The more relevant the comparison properties are to the target properties, the stronger the argument. Here is an example of an analogical argument which lacks relevance. "Book A and Book B both have a hardbound cover, pages, words on the pages and numbers at the bottom of the pages. Book A is a boring story. Therefore we can assume that Book B has a boring story." Though I have given a number of similar properties between Book A and Book B, none of these properties are relevant and thus do nothing to increase the probability that Book B is boring.

Number - The more properties two things share in common with each other, the stronger the argument. This is based on the notion that the more two things are alike, the more likely they also share the property stated in the conclusion. As stated above, relevance plays a key role in determining how much weight these similarities are given.

Disanalogy - Relevant disanalogies or dissimilarities must also be considered when determining the strength or weakness of an analogy. For example if I say, "I have known three people who have had surgery at this hospital with the same surgeon and they have all turned out successfully. Therefore Jane's surgery will also be a success." But what if the three success stories all had minor surgery and Jane is scheduled for a high risk procedure? This of course would be a very relevant disanalogy.

Critical Thinking Web: Analogical Arguments
PHIL 1500: Dr. Donald Nute: Unit 3: Analogical Arguments

Monday, May 18, 2015

Hasty Generalization

The hasty generalization is an informal fallacy in which an inductive generalization is made from a sample that is inadequate to support the generalization in the conclusion. As discussed in the post on inductive generalization, this may be because the sample is too small or biased.

Hasty generalizations often result from anecdotal arguments, which are short stories typically taken from the personal experience of the arguer. Generally, these anecdotal arguments describe only one or a few episodes which are then used to generalize about the population.

For example:

"Acupuncture works. My friend Tom tried it and he said it cured his back pain.".


"Smoking isn't harmful. My dad smoked a pack a day and lived until 95."

The Nizkor Project: Hasty Generalization
Fallacy Files: Hasty Generalization

Thursday, May 14, 2015

Inductive Generalization

An inductive generalization is an argument that moves from particular premises to a generalized claim. As defined by Trudy Govier "In inductive generalizations, the premises describe a number of observed objects or events as having some particular feature, and the conclusion asserts, on the basis of these observations, that all or most objects or events of the same type will have that feature."

P1 - Pavlovian conditioning caused dog Fido to salivate when a bell rings.
P2 - Pavlovian conditioning caused dog Rover to salivate when a bell rings. 
P3 - Pavlovian conditioning caused dog Spot to salivate when a bell rings.
P4 - (etc.)
C - Therefore, Pavlovian conditioning causes all dogs to salivate when a bell rings.

It seems intuitive that the strength of the example above largely relies upon how many particular instances Pavlovian conditioning resulted in a dog salivating. A thousand instances of a salivating dog would be a stronger argument than only ten instances. This leads us to the concept of sample.

"In inductive generalizations, features that have been observed for some cases are projected to others. Following established practice in statistics and in science, we call the observed cases the sample and the cases we are trying to generalize about the population." Statistical sampling methodologies are beyond the scope of this post but the basic idea is that the strength of an inductive generalization largely depends on sample size and how representative it is.  

In general, increased sample size is associated with a decrease in sampling error as it is more likely to represent the population (though there are diminishing returns). For more on why this is so, see the law of large numbers and central limit theorem.

A representative sample is one in which the selected segment closely parallels the whole population in terms of the characteristics that are under examination (for example, if one third of the population has relevant characteristic X, then one third of the sample should have characteristic X). We try to make samples representative by choosing them in such a way that the variety in the sample will reflect variety in the population.

Sampling methods include Random Sampling, Stratified Sampling, Systematic Sampling, Convenience Sampling, Quota Sampling and Purposive Sampling.

Monday, May 11, 2015

Induction: Inductively Strong & Inductively Cogent

Induction is the process of reasoning from one or more premises to reach a conclusion which is likely, though not certainly true. Hence, ainductive argument is one in which if the premises were true, then the conclusion is likely to be true.

"In the most general sense, Inductive reasoning is that in which we extrapolate from experience to what we have not experienced. The assumption behind inductive reasoning is that known cases can provide information about unknown cases."1 Grover goes on to describe inductive arguments as having the following characteristics:

1. The premises and the conclusion are all empirical propositions.
2. The conclusion is not deductively entailed by the premises.
3. The reasoning used to infer the conclusion from the premises is based on the underlying assumption that the regularities described in the premises will persist.
4. The inference is either that unexamined cases will resemble examined ones or that evidence makes an explanatory hypothesis probable.

Inductively Strong Arguments - An inductively strong (forceful) argument is one in which, if the premises were considered to be true, the conclusion is probably true. In other words, if we assume the premises are true the likelihood that the conclusion of an inductively strong argument is true is greater than 50%. If the probability that the conclusion is true is 50% or less, than the argument is inductively week.

Inductively Cogent Arguments - An inductively cogent argument is one which is inductively strong and all of its premises are actually true. 

To fit into our informal logic model, instead of requiring that the premises be true we would require that they be acceptable. This, of course, is due to the difficulty often encountered in establishing with certainty whether or not something is true. 

Types of inductive arguments include inductive generalization, statistical syllogism and analogical arguments.

1 A Practical Study of Argument

Critical Reasoning and Philosophy, A Concise Guide to Reading, Evaluating, and Writing Philosophical Works 

Probability and Induction

Thursday, May 7, 2015


An outline is a method of presenting the main and subordinate ideas of a document by organizing them hierarchically.

Alphanumeric outline
An alphanumeric outline uses Roman numerals, capitalized letters, Arabic numerals and lowercase letters as prefix headings. 

The Chicago Manual of Style (CMS) uses the following outline format:

I. (Roman numeral) 
     A. (Capital letter) 
          1. (Number) 
               a) (Lowercase letter followed by closing parenthesis) 
                    (1) (Number enclosed in parenthesis) 
                         (a) (Lowercase letter enclosed in parenthesis) 
                              i) (Roman numeral with lowercase letters followed by a closing parenthesis)

The Modern Language Association (MLA) uses essentially the same method except the first lowercase letter is followed by a period instead of a closing parenthesis.

Decimal outline
The decimal outline uses only numbers as prefix headings making it easier to see how every item relates within the hierarchy. It uses the following outline format:

Here is a sample decimal outline:

1.0 Choose Desired College
     1.1 Visit and evaluate college campuses 
     1.2 Visit and evaluate college websites 
          1.2.1 Look for interesting classes 
          1.2.2 Note important statistics

Wednesday, May 6, 2015

Favorite podcast episodes

Here are some of my favorite podcast episodes. I've been listening to podcast for years and continue to, so I'll be adding newly and rediscovered favorites.

Love+Radio: The Living Room (Emotionally Stirring, Thought Provoking)

Radiolab: Season 7, episode 1
Animal Minds
-Animal Blessings
-Spindle Cells
-Sharing is Caring? Or is it a Sin?

Radiolab: Season 7, episode 2
Lucy (Emotionally Stirring, Thought Provoking)

Radiolab: Season 3, episode 4
Part 3: Clive

Radiolab: Season 12, episode 2

Rationally Speaking 134
Michael Shermer on: "Science drives moral progress"

Invisibilia: Episode 1
-Dark Thoughts (Thought Provoking, Psychological) 
-Locked-In Man (Emotionally Stirring, Thought Provoking, Psychological)

Freakonomics: When Willpower Isn't Enough
-temptation bundling

Econtalk: Phil Rosenzweig on Leadership, Decisions, and Behavioral Economics

Tuesday, April 21, 2015

Kentucky: Neither straights or gays can marry the same sex so ban is not discriminatory

It's been reported that the administration of Kentucky Governor Steve Beshear has filed a brief with the US Supreme Court defending it's ban on gay marriage. In it they argue
"Kentucky’s marriage laws treat homosexuals and heterosexuals the same and are facially neutral. Men and women, whether heterosexual or homosexual, are free to marry persons of the opposite sex under Kentucky law, and men and women, whether heterosexual or homosexual, cannot marry persons of the same sex under Kentucky law,"
I'll be a bit more generous than some of the news outlets that reported on this by noting that the brief is  42 pages so there may or may not be other more rational arguments presented (I didn't take the time to read it). Regardless, it is hard to believe that the argument above could possibly be presented as a serious justification for upholding it's ban on gay marriage.

Imagine a law which states that it is now illegal to practice Christianity and then arguing that it doesn't discriminate against those who are Christian because it also applies to Muslims, Buddhist, and atheist. This sort of specious legal reasoning really drives me crazy. I can't imagine that the Supreme Court will give it any credence.

HuffPo: Kentucky: Our Same-Sex Marriage Ban Isn't Anti-Gay Because It Applies To Straight People, Too

Thursday, March 19, 2015

Dragon Ball Z: Light of Hope

A very impressive fan film adaptation of "The History of Trunks" TV-Special that is part of the Dragon Ball Z cartoon series. You can read more about it here. Looking forward to the next installment.