Text Table of Contents #4:

What are the Reasons?

Arguments intend to convince us to accept a conclusion – i.e., a position, claim, belief, etc.

Why does the author want us to accept this conclusion?

Reasons tell us why that conclusion should be accepted.

Will Ferrell

For each sentence ask:

◦Does this sentence support the conclusion?

Or does it make sense when you precede the sentence with:

◦The conclusion is true because …

Reasons + Inferences Conclusion

The acceptability of a conclusion depends on◦ the quality of the reasons (evidence)◦ the validity of the inferences (logic)

Infer deduce or conclude (information) from evidence and reasoning rather than from explicit statements (Oxford dictionary)

Inference is the “connection” between the reason and the conclusion.

Validity of inference◦ does not refer to truth of premise or conclusion◦ refers to the form of the inference◦ i.e., how the inference is drawn

A word about inference - induction vs. deduction induction – results in probable conclusion deduction results in certain conclusion

People who forecast the weather (meteorologists) are well educated. The weather forecasts for the past 200 days have been 85% accurate. The forecasts for the past 11 days have predicted hot weather and each day the temperature was at least 88 degrees. The forecast for tomorrow is for the weather to be hot. Therefore, the weather tomorrow will probably be hot.

1. People who forecast the weather (meteorologists) are well educated.

2. The weather forecasts for the past 200 days have been 85% accurate.

3. The forecasts for the past 11 days have predicted hot weather and each day the temperature was at least 88 degrees.

4. The forecast for tomorrow is for the weather to be hot.

Conclusion:Therefore the weather tomorrow will probably be hot.

UH Hilo should increase the tuition rate charged per credit. Many college scholarships never get awarded because students don’t apply for them. Also, the added funding would allow UHH to hire more faculty and offer more courses which would decrease the number of semesters for graduation for many students.

1. Many college scholarships never get awarded because students don’t apply for them.

2. Also, the added funding would allow UHH to hire more faculty and offer more courses which would decrease the number of semesters for graduation for many students.

Conclusion:• UH Hilo should increase the tuition rate charged per credit.

All fruits are sweet. A banana is a fruit. Therefore, a banana is sweet.

For the conclusion to be necessarily true, the premises need to be true.

Leading from true premises to a false conclusion.

All apples are fruit. (correct) Bananas are fruit. (correct) Therefore, bananas are apples. (incorrect)

Do you understand why this argument is invalid?

When a valid argument is used to derive a false conclusion from false premises, the inference is valid because it follows the form of a correct inference.

A valid argument with false premises may lead to a false conclusion:◦ All tall people are Greek. (incorrect)◦ John Lennon was tall. (correct)◦ Therefore, John Lennon was Greek. (incorrect)

Do you understand why this argument is valid?

A valid argument can also be used to derive a true conclusion from false premises:◦ All tall people are musicians (incorrect)◦ John Lennon was tall (correct)◦ Therefore, John Lennon was a musician (correct)

Do you understand why this argument is valid?

Facts, examples, analogies, statistics, authorities, etc.

Observations, beliefs, principles

Later we will explore more thoroughly how to evaluate the quality of evidence