August 29th, 2016 (Permalink)

Don't Check it Out, Too

I have a book review of Scrutinizing Argumentation in Practice, edited by Frans van Eemeren and Bart Garssen, in the latest issue of the journal Cogency. The book is a collection of scholarly conference papers, so probably not of interest to the casual or beginning student of argumentation. However, if you're interested in taking a deeper dive into the topic, do check it out.

Source: Gary N. Curtis, "Review of Scrutinizing Argumentation in Practice", Cogency, Vol. 8, No. 1 (111-121), Winter 2016 (PDF)

August 24th, 2016 (Permalink)

Don't Check it Out

Brian "Skeptoid" Dunning has a new podcast about the meme that says you shouldn't criticize something unless you've tried it. The title for this entry doesn't refer to the podcast: Do check it out!

The meme is quite obviously not generally good advice: I've never jumped out of an airplane without a parachute, but I'm rather critical of the idea. I'm sure that the first few seconds are thrilling; it's what comes after that concerns me.

I generally agree with Dunning, but would like to add my own take on this, relating the issue more explicitly to the three logical fallacies that Dunning alludes to:

  1. Post Hoc: The sort of things that people keep telling Dunning to shut up about unless he's tried them are "alternative" medical treatments and the like. The trouble with evaluating such treatments by trying them is that most medical problems will eventually improve on their own, so if you try some new "treatment" you may well improve for reasons having nothing to do with the treatment.

    The post hoc effect can even go the opposite direction: I recently began a course of treatment with a daily medication that I had never taken before. Shortly after beginning the new treatment, I experienced extreme back pain. This led me to wonder whether the pain was caused by the medication, though this was not a known side effect. Fortunately, the pain went away after a few hours and was probably due to raking the yard rather than the new medication. However, the coincidence of the pain occurring so soon after starting the medicine was compelling enough to cause me to temporarily stop taking it.

    One thing that Dunning says that I disagree with is the following: "Crediting something with efficacy because it appeared to work when you tried it is a perfectly rational conclusion for an intelligent person to make." If you substituted the word "normal" for "rational", I would agree. It's normal for people to think that way, just as I did when I hurt my back, but it ain't rational. That's why the post hoc fallacy is such a common one. Moreover, it's often just plain impossible for us to tell what caused what, especially when you're talking about health. Viruses and bacteria are too small to see, and you generally can't see inside your own body to tell what's going on in there. That's what you need science for.

  2. Hasty Generalization: You're only one data point. Even if you have experienced something, you shouldn't generalize from the experience of just one person, even if that person is you―that's as hasty a generalization as you can get. Just because something "worked" for you doesn't mean that it will "work" for anyone else, so you shouldn't generalize to other people. Not only that, but just because something worked in the past doesn't mean that it will work in the future, so you shouldn't even generalize for your future self on the basis of just one past experience.
  3. The Anecdotal Fallacy: The anecdotal fallacy is the tendency for a vivid anecdote―or story―to overwhelm other and better evidence, and what could be more vivid than your own experience?

Source: Brian Dunning, "Don't Try It Before You Knock It", Skeptoid, 8/23/2016

August 17th, 2016 (Permalink)

Lesson in Logic 13: Categorical Statements

A categorical statement is one that asserts something about a category, that is, a class or type of thing. Classes are talked about using class terms, which are common nouns or noun phrases.

Examples of class terms: "shoes", "ships", "cabbages", "kings", "pileated woodpeckers"

As mentioned in lesson 11―see the Previous Lessons, below―classes need not have members, and some class terms refer to such empty classes.

Examples of empty class terms: "unicorns", "vampires", "werewolves", "passenger pigeons"

Moreover, there also terms for classes about which we may not know whether they are empty or not.

Examples: "bigfeet", "Loch Ness monsters", "ivory-billed woodpeckers"

The simplest categorical statements are those that talk about a single class, and thus contain a single class term. The simplest thing that you can say about a single class is that it is non-empty or empty, that is, that something of that type exists or does not exist. You learned in a previous lesson how to represent on a class diagram that a single class is empty or non-empty by using shading to represent emptiness and an "X" to represent a non-empty class.

The type of categorical statements that you will learn about in this lesson contain two class terms, but representing them on a two-circle Venn diagram is a simple extension of what you've already learned. There are four types of such statements that are studied in traditional logic and designated by the letters: A, E, I, and O. The I and O type of statement say something about "some" member of the subject class, so an "X" is used to indicate that a subclass is non-empty. Venn Diagram for I Proposition

I: An I statement has the form: "Some A is a B".

Example: Some arguments are syllogisms.

There are many ways to express I statements in English, including: "some As are Bs", "there are As that are Bs", etc. This type of statement relates two classes by asserting that at least one member of the first class, A, is also a member of the second class, B. To use a Venn diagram to represent this information you need to show that there is something in A that is also in B, that is, that something is in the overlap of the two classes.

The A and E types of statement assert that a certain subclass is empty, so you will need to use shading instead of an "X". Venn Diagram for E Proposition

E: An E statement has the form: "No A is a B".

Example: No bats are birds.

There are many ways to express E statements in English, such as "no As are Bs", as in the Example. This type of statement relates two classes by asserting that no member of the first class, A, is a member of the second class, B. E statements are the opposite of I statements in that the I asserts that there is something in the overlap of the two classes, whereas the E asserts that there is nothing there. Thus, to represent this information on a Venn diagram we need to show that there is nothing in A that is in B, that is, that the overlap area is empty. So, instead of an "X", you shade in the overlap as shown.

Exercises: If you understand how to represent the I and E statements on Venn diagrams, you should be able to figure out how to represent the other two traditional categorical statements. For the following two exercises, draw the primary diagram and label the circles "A" and "B", then use either an "X" or shading to indicate that a subclass in the diagram is either non-empty or empty:

  1. "Some A is not a B."
  2. "All As are Bs."

Answers to the Exercises

In the next lesson, you'll learn how to use these diagrams to determine logical relationships between these four types of categorical statement.

Previous Lessons:

August 12th, 2016 (Permalink)

You May Need a Napkin

Check out this quote from the beginning of a New York Times editorial:

Global trade allows Americans to satisfy their appetites for strawberries in spring, apples in midsummer and asparagus in autumn. … But getting fresh produce year round also means that consumers are exposed to foreign food production systems that may not be well regulated. Although the vast majority of the 30 billion tons of food imported annually is wholesome, recent incidents of illness caused by tainted Guatemalan raspberries…have made food safety a public concern.
Source: "Safety Standards for Imported Food", International New York Times, 10/3/1997

Is there anything there that grabs your attention? Something that makes you feel a bit doubtful―a little skeptical? No?

How about the claim that "30 billion tons of food [is] imported annually". If you're like me, you have no idea how much food is imported into the United States on a yearly basis. In fact, you may have no notion of even a ballpark figure; is it millions or billions of tons? Do you have a sense of how much food a ton is? I wouldn't blame you if you just read over that claim with glazed eyes and didn't think about it at all. You probably would just accept it because it is the Times, after all, and surely they know what they're talking about.

Don't do that, because this is a claim that you can easily test yourself. I'm not talking about doing research on how much food is imported annually. No, I'm talking about doing a simple back-of-the-envelope calculation (BOTEC) to test the claim for sanity. Such calculations are called "back-of-the-envelope" because they are short and simple enough to be scribbled on an envelope or even a cocktail napkin.

How do you do such a test? Here's a hint: use elementary math together with what you already know―that's all you'll need. Try to transform a number that is too big to grasp into one that you can evaluate using common sense.

Give it a try, then click on the link below when you think you've figured it out.

Go to the Back of the Envelope

August 11th, 2016 (Permalink)

New Book: A Survival Guide to the Misinformation Age

I haven't read the new book with the above title, so this is not an endorsement―just a notice. The author is David J. Helfand, an astronomer, which presumably explains its subtitle: Scientific Habits of Mind. I could certainly use a survival guide to misinformation, and this one appears promising. Judging from the chapter titles, the book has sections on the following topics:

I'm especially excited to see a chapter on back-of-the-envelope calculations (BOTECs) (ch. 4), since I've complained for years that they are an important skill that books and courses on logic and critical thinking fail to teach. Some of the misinformation that inundates us every day can be debunked with a BOTEC, so that one doesn't need to do any research to show that it can't be true. This book may be worth getting for that chapter alone.

August 6th, 2016 (Permalink)

The Second Puzzle of the Sleeper Cells

The Agency for Counter-Terrorism (ACT) has again discovered the existence in a target country of a sleeper cell of agents of a second foreign power―see the Previous Puzzle, below, for the first case. Once again, I cannot here reveal the names of either the target country or the foreign power. In addition to discovering the cell, the ACT recovered a secret document outlining the strict rules used by this power in its sleeper cell operations in target countries. According to the secret document, this second power did not use the set of four rules that the first power used. Instead, it used the following two rules:

  1. "The membership rule": Every sleeper agent belongs to exactly two cells.
  2. "The overlap rule": Any two cells have exactly one sleeper in common.

These rules are rigidly adhered to, and the foreign power would shut down its entire sleeper operation rather than violate a rule. In addition, the secret document reveals that the power currently has exactly five cells in the target country. Of course, what ACT would most like to know is just how many sleeper agents they should look for. Can you help? Can you determine from the above information what is the exact number of sleeper agents there are in the target country?


Previous Puzzle: The Puzzle of the Sleeper Cells, 2/29/2016

August 1st, 2016 (Permalink)


McDonald’s Nixing Some Unpalatable Ingredients

Only "some"? That could explain a lot.

July 31st, 2016 (Permalink)

An Average Puzzle

Here's a puzzling pair of facts:

  1. The average annual salary for a mayor in the United States is $62,000.
  2. The average annual salary for a deputy mayor in the U. S. is $83,000.

So, suppose you have your choice between being mayor or deputy mayor of a city, which should you choose, assuming that your only concern is money?


July 16th, 2016 (Permalink)

Lesson in Logic 12: Two-Circle Venn Diagrams

The previous lesson explained how circles can be used to represent classes and how Venn diagrams show that a class is empty or non-empty. If you haven't learned that lesson or don't already understand how circles represent empty or non-empty classes, you should start with the previous lesson―see the link, below. The Primary Diagram

In this lesson, we will add an additional circle and see how logical relations between two classes are represented in Venn diagrams. Venn's innovation was to realize that two overlapping circles, which he called "the primary diagram", can be used to represent the basic logical relations between two classes―see the diagram to the right. All two-circle Venn diagrams start with the primary diagram.
2-circle Venn diagram

As you learned in the previous lesson, a single class circle divides the universe of things into two subclasses: those things that belong to the class and those things that do not belong to the class; the former occupy the interior of the circle and the latter lie outside it. In the primary diagram there are two circles representing two distinct classes―let's call them "A" and "B". The primary diagram divides the entire universe into four subclasses: things that are A but not B, things that are B but not A, things that are both A and B, and things that are neither A nor B. Letting the left circle represent A and the right B, the diagram to the right shows which sections of the circles represent each of the four subclasses.

Exercise 1: Draw a primary diagram and label one of the circles "Birds" and the other "Flying Animals". Now, indicate on the diagram where you would find a robin, a penguin, a bat, and yourself.

So far, the two-circle diagrams that you have seen don't say anything about the relations between the two classes. However, to say something about the logical relations between classes, you will use the same system of shading a subclass to indicate that it is empty and marking one with an "X" to show that it's not empty. If you understand the class regions of the two-circle diagram as tested in the above exercise, and if you know how to use shading and Xs to represent empty or non-empty regions, then you should be able to do the following exercise.

Exercise 2: Start by drawing the primary diagram, then label one circle "Mammals" and the other "Bats". Now, represent that the class of bats that are not mammals is empty. Also, represent that the class of mammals that are not bats is non-empty.

In the next lesson, you will learn how to use the two-circle diagram to represent statements about the logical relationships between two classes.

Answers to the Exercises

Source: Sun-Joo Shin, Oliver Lemon & John Mumma, "Venn Diagrams", Stanford Encyclopedia of Philosophy, 2013

Previous Lesson: Lesson in Logic 11: Class Diagrams, 6/22/2016

July 2nd, 2016 (Permalink)

New Book: Everydata

A new book by John H. Johnson and Mike Gluck is called Everydata: The Misinformation Hidden in the Little Data You Consume Every Day.

What's up with that title? Here's what they say about it:

Everydata isn't a real word. Not yet, anyway. We made it up to describe the tons of data that you encounter every day. (Preface)

So, "everydata" appears to be a portmanteau word combining "everyday" with "data", and thus short for "everyday data". I don't much care for the word―so I hope it never actually becomes a "real word"―but the topic, which the Preface describes as follows, sounds intriguing:

Every day, you're surrounded by media reports and other sources that are often filled with hidden information―and misinformation. This book will help you to identify it, interpret it, and become an educated consumer of data…. (Preface)

Using Amazon's "Look inside!" feature to glance through it, the book appears to cover such topics as sampling, averages, correlation and causation, polling, and cherry-picking. These should be familiar topics to regular readers of this site, but it's good to see them reaching a wider audience. Also, it sounds rather like last month's new book (see the Resource, below), but there's certainly enough grist for two mills.

Johnson is an economist and statistician, so he should know how to interpret everyday data; and Gluck is a writer, so he should know how to, well, write. I'm going to aim for reviewing it here next month.

Resource: New Book: Truth or Truthiness, 6/18/2016

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