Logical thinking 2 True in part, true for the whole

Generalizing about groups or properties can be problematic

Using sound logic is vital for advanced communication, it will also help you answer questions clearly in meetings, presentations and conversation. It will also help you get better scores on logical aspects of English speaking tests.

Introduction

We'll look at how people can confuse specific information with general information, and we will discuss ways to accurately attribute information.

Warm Up

A man reasoned that since we can't see atoms, and you are made of atoms, you must be invisible.

We can agree that he is incorrect, but why is he incorrect?

The man has generalized about the properties of atoms.

Point out that it's easy to refute the conclusion (because you are visible)

It's important to refute the premise: The fact that we can't see them with our naked eyes doesn't mean that they are  invisible. If we look at atoms through a powerful microscope, then we can see them. Just because we can't see them now, doesn't mean they are invisible.

The phrase "we can't see atoms" is a bit of a generalization. Better to say "we can't see individual atoms without a microscope."

Language

Let's talk about generalizing. When something is true for the whole, it may or may not be true for one part, and vice versa. For example:

Japanese people eat rice, and Junko is Japanese, so Junko definitely eats rice.

Do you think this is fair?

To point out a fallacy, You can start with these kind of phrases:

  • I don't think it's safe to say...
  • Actually I don't think...
  • I'm not sure I agree that...

We can, however, draw tentative conclusions. Imagine Junko is coming to your house for dinner, and you are thinking about making a rice dish. Would you ask Junko if she eats rice, or would you assume that she does? To discuss generalizations, we can use these phrases:

  • In general...
  • From my understanding/ experience...
  • As far as I know...
  • I think we can agree that...
  • ...most...
  • ...nearly all...

Discuss properties of groups in general with your instructor. What can you say about people who live in your area?

In the Junko example, discuss each point: "Do Japanese people all eat rice?" ... "are we sure that Junko is Japanese?" ... "so it is clear that she eats rice?"

People who live in your area:

  • are they loud/ quiet/ polite?
  • language (do they speak Japanese?)
  • eating habits (do they eat rice? bread? spicy food?)

Just, needless to say, don't be be racist.

You can tell your student these Practice phrases may not be necessary if you are dealing with complex arguments. However, for this practice, we can use them. Ask the student to correct the argument about Junko. It could end up something like this:

In general, Japanese people eat rice, and as far as I know Junko is Japanese, so I'd say Junko probably eats rice.

Practice

Try to refute and clarify these arguments. Is it true in part, completely true, or completely false?

  1. Cows are black and white. My cup is black and white. Therefore, my cup is a cow.
  2. Fuel costs have been decreasing, so it's safe to say that the price of airplane tickets will decrease in the foreseeable future.
  3. Marc Jacobs clothing is expensive, and that person's shirt says "Marc by Marc Jacobs" so the person must have paid a lot for their shirt.