Negative Necessary Condition Tests

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En provenance du cours de Duke University

Think Again III: How to Reason Inductively

127 notes

Duke University

Think Again III: How to Reason Inductively

127 notes

How to Reason Inductively Think Again: How to Reason and Argue Reasoning is important. This series of four short courses will teach you how to do it well. You will learn simple but vital rules to follow in thinking about any topic at all and common and tempting mistakes to avoid in reasoning. We will discuss how to identify, analyze, and evaluate arguments by other people (including politicians, used car salesmen, and teachers) and how to construct arguments of your own in order to help you decide what to believe or what to do. These skills will be useful in dealing with whatever matters most to you. Courses at a Glance: All four courses in this series are offered through sessions which run every four weeks. We suggest sticking to the weekly schedule to the best of your ability. If for whatever reason you fall behind, feel free to re-enroll in the next session.We also suggest that you start each course close to the beginning of a month in order to increase the number of peers in the discussion forums who are working on the same material as you are. While each course can be taken independently, we suggest you take the four courses in order. Course 1 - Think Again I: How to Understand Arguments Course 2 - Think Again II: How to Reason Deductively Course 3 - Think Again III: How to Reason Inductively Course 4 - Think Again IV: How to Avoid Fallacies About This Course in the Series: Think Again: How to Reason Inductively Want to solve a murder mystery? What caused your computer to fail? Who can you trust in your everyday life? In this course, you will learn what distinguishes inductive arguments from deductive arguments and then how to analyze and assess five common forms of inductive arguments: generalizations from samples, applications of generalizations, inference to the best explanation, arguments from analogy, and causal reasoning. The course closes by showing how probability can be used to help us make decisions of all sorts. Suggested Readings Students who want more detailed explanations or additional exercises or who want to explore these topics in more depth should consult Understanding Arguments: An Introduction to Informal Logic, Ninth Edition, Concise, Chapters 8-12, by Walter Sinnott-Armstrong and Robert Fogelin. Course Format Each week will be divided into multiple video segments that can be viewed separately or in groups. There will be short ungraded quizzes after each segment (to check comprehension) and a longer graded quiz at the end of the course.

À partir de la leçon

Causal Reasoning

<p><b>CONTENT</b>: This module will focus on how to decide what causes what. Students will learn how to distinguish necessary conditions from sufficient conditions and how to use data to test hypotheses about what is and what is not a necessary condition or a sufficient condition. Then we will distinguish causation from correlation (or concomitant variation) and explain the fallacy of post hoc ergo propter hoc. It is sad that some diners had to die to make this lesson possible, as you will see.</p> <p><b>LEARNING OUTCOMES</b>: By the end of this week’s material you will be able to do: <ul> <li> analyze causal reasoning</li> <li>distinguish necessary from sufficient conditions</li> <li>determine what is necessary or sufficient for what</li> <li>separate causation from correlation</li> </ul> </p> <p><b>OPTIONAL READING</b>: If you want more examples or more detailed discussions of these topics, we recommend <em>Understanding Arguments, Ninth Edition</em>, Chapter 10.</p>

Negative Sufficient Condition Tests9:28

Positive Sufficient Condition Tests10:09

Negative Necessary Condition Tests4:36

Positive Necessary Condition Tests6:51

Complex Conditions11:39

Rencontrer les enseignants

Dr. Walter Sinnott-Armstrong
Professor
Philosophy
Dr. Ram Neta
Professor
Philosophy

Last time we looked at sufficient condition tests and they

tell us what is or is not a sufficient condition.

But we also need to know which

factors or features or candidates are necessary conditions.

So this time, we're going to look at necessary condition tests.

And as with sufficient condition tests, there's going to be 2 of them.

There's a negative

necessary condition test that tells you what

is not a necessary condition, and then there

will be a positive necessary condition test

that tells you what is A necessary condition.

So first, the negative necessary condition test.

It says simply that x is not a necessary condition of y, if there's any

case where x is absent and y is present. Because to be a necessary

condition it has to be the case that whenever, x is absent, y is absent too.

So if there is even one case, where X is absent and Y is present, that's

a counterexample to the universal claim that whenever, that is in all cases X's.

Where x

is absent, y is absent, okay? So let's apply this to our data so far.

But let's look first, just at the first 3 people Ann, Barney, and Cathy.

You remember them from last time, they were at the banquet.

Is pie a necessary condition of death, well,

is there a case where pie is absent and

death is present? Yes.

That means that pie is not a necessary condition of death.

Which case shows us that?

Well, it's Barney. Notice that it's not and.

Some people get confused about this, but what and

tells us is that pie is not sufficient for death.

It's Barney that tells

us that pie is not necessary for death

because with Barney, you get death without pie.

So pie was not necessary.

For Barney to die.

So it's the cases of death that made Barney out

of these 3 to tell us what's not necessary for death.

Now, the case of Barney also tells us

that another dessert is not necessary for death.

Which one

is that? Ice cream.

because Barnie also didn't have ice cream, and he died, so he

died without having ice cream, so ice cream is not necessary for death.

So, what might be necessary for death?

Tomato soup might be necessary for death, because out of

these 3 cases, there's nobody who dies without having tomato soup.

Fish might be necessary for death.

because out of these cases, there's nobody that dies without having fish.

Red wine might be necessary. And cake might be necessary.

Because Barney's the only one who dies, all

of those things still might be necessary for death.

And the only way to rule out some of those candidates so as to narrow down the field.

Is to get more data. So remember Doug and

Emily, our old friends from the banquet.

What do they show us? Is cake necessary for death?

No, because now we have a case where someone died without

eating cake. Namely, Emily.

And is fish necessary for death? Oh, well

both Emily and Barney had fish. So there is nobody that dies

without having fish. So, so far on this data.

It looks like fish still might be a necessary condition for death.

So, since it's survived this far, I guess we

can conclude that fish is a necessary condition for death.

No way, because remember, this is just the negative necessary condition test.

It tells us what is not a necessary condition.

We still are not in a position to

conclude that fish is a necessary condition for death.

For that, we'll need to look at the positive necessary condition test.

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