Critical Thinking by Example

Chapter 8: Accepting Premises: Questions of Logic and Language

Material covered in this chapter 8.1 Fallacies in accepting premises 8.2 Logical considerations in accepting premises 8.3 Considerations of language in accepting premises

Recall that we said that with good arguments it is possible to answer “yes” to each of these questions:

1. Assuming that the premise set is acceptable, is the premise set relevant to the conclusion?
2. Assuming that the premise set is acceptable, does the premise set provide sufficient support for the conclusion?
3. Is the premise set acceptable?
A bad argument is one that answers “no” to one or more of these questions. In this chapter and the next we will examine arguments where the answer to question 3 is “no”. Since question 3 is so broad, I propose that we subdivide it into these two questions:
Is the premise set logically and linguistically acceptable?
Is the premise set evidentially acceptable?
In this chapter we will deal with the former question. I will first list some fallacies, and then discuss some general strategies for thinking about whether premises are logically and linguistically acceptable.

8.1 Logical and Linguistic Fallacies in Accepting Premises

Fallacy of Begging the Question This fallacy is present when the conclusion is the same as a premise. In example 8.1, the conclusion and the premise are the same despite the different wording: ‘Darwinianism’ is simply another name for the ‘theory of natural selection’.	Example 8.1 “You should believe in Darwinianism because the theory of natural selection is true.”