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Critical Thinking By Example

 Chapter 5: Intermediate Standardizing
  Quiz 5.11 Quiz 5.2 Quiz 5.3 Quiz 5.4 Quiz 5.5

Material covered in this chapter

  •     5.1 Premise and conclusion indicators

  •     5.2 Missing premises

5.1            Premise and Conclusion Indicator Words

Thus far we have dealt with fairly simple and straightforward arguments. In this chapter you will learn techniques for standardizing more complex arguments. The task of standardizing requires us to “get inside the heads” of the persons making the argument. We want to figure out what point they intend to support (the conclusion), and what reasons (premises) they intend to offer. There is no infallible way of ascertaining intentions. We have all had the experience of misinterpreting others, e.g., not realizing that someone was joking. One good indicator of the authors’ intentions is premise and conclusion indicators: words used to signal premises and conclusions. Here is a list of some conclusion indicators:

 

Therefore

For all these reasons

Thus

On these grounds it is clear that

So

Consequently

Hence

Proves that

Then

Shows that

It follows that

Indicates that

In conclusion

We can conclude that

Accordingly

Means that

Demonstrates that

Suggests that

 

Here is a list of premise indicator words:

 

Since

On the grounds that

Because

For the reason that

For

As indicated by

Follows from

May be inferred from

As shown by

May be derived from

Given that

May be deduced from

A word of warning: sometimes the words in these lists may be used in other ways. Consider the following two examples:

 

Example 5.1: The word ‘since’ as a premise indicator

You should go to class today since there is a quiz.

 

Example 5.2: The word ‘since’ not used as a premise indicator

There has been no good music since the great music of the 1960s.


The word ‘since’ is on our premise indicator list. This suggests that we might standardize 5.1 thus:

P1: There will be a quiz today.

C: You should go to class.

This is a good reconstruction of the author’s thinking. The same can’t be said of the same reconstruction of 5.2:

P1: The great music of the 1960s.

C: There has been no good music.

There are obvious problems with this reconstruction, including the fact that P1 is not even a complete thought. The difference in the two examples is that the word ‘since’ is used as a premise indicator in 5.1 but in a temporal (i.e., time) sense in 5.2. A good trick to see if words on these lists are being used as premise or conclusion indicators is to try substituting a different word from the lists. If you can do so without altering the meaning of the passage, then it probably is a premise or conclusion indicator. If not, then it is probably not a premise or conclusion indicator. Thus, in 5.1 we can take out ‘since’ and substitute ‘because’ with no change in meaning. However, in 5.2 this same substitution will not work (in fact the sentence does not even make sense with this substitution).

5.2 Missing Premises and Conclusions

Premises and conclusions are sometimes not stated in an argument. Standardization requires that we identify any missing premises or conclusions, for only in this way can we properly evaluate an argument. Consider example 5.3:

 

 

Example 5.3: An argument with a missing premise.

Donald Trump is a capitalist. So, Donald Trump must die.

 

We can standardize the stated premise and conclusion thus:

P1: Donald Trump is a capitalist.

C: Donald Trump must die.

It is clear that there is a missing premise in this argument, for the stated premise seems to offer no support for the conclusion. Clearly the author must have some further thought in mind; something along the lines of: “All capitalists must die”.  So, a complete standardization is as follows:

P1: Donald Trump is a capitalist.

MP2: All capitalists must die.

C: Donald Trump must die.

‘MP’, of course, stands for ‘missing premise’. The importance of supplying the missing premise clearly helps with the evaluation of this argument: the premises are relevant and sufficient for the conclusion, but MP2 is clearly problematic. By supplying the missing premise we are able to see exactly what is wrong with the argument.

Similarly, if the author had said: “Donald Trump is a capitalist, and all capitalists must die” we should construe this as an argument with a missing conclusion: MC: Donald Trump must die.

Arguments may have missing premises and conclusions; consider example 5.4:

 

Example 5.3: An argument with a missing premise and missing conclusion.

Background: Local government officials are considering changing the legislation to make all elective abortions illegal. Smith wrote a letter to the editor in support of changing the legislation. Jones responds with her own letter to the editor, a single sentence:

Argument: “If the government makes all elective abortions illegal, we will live in a less just society.”

 

This single sentence is best understood as an argument with a missing premise: “We don’t want to live in a less just society”; and a missing conclusion: “The government should not make all elective abortions illegal”. We would standardize it thus:

MP1: We do not want to live in a less justice society.

P2: If the government makes all elective abortions illegal, we will live in a less just society.

MC: The government should not make all elective abortions illegal.

d
d

d


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