Identifying and Evaluating Arguments

Flat Earth Map
A “flat-Earth” map drawn by Orlando Ferguson in 1893.

Week 3, Lecture 2

Learning Objectives

  1. Identify the structure of and categories of arguments
  2. Explain how to evaluate arguments

What is the structure of an argument?
Reason (also called a premise, or evidence) + reason (also called a premise, or evidence) —> conclusion

What are the categories of arguments?

  • Deductive: Conclusion follows necessarily from premises (reasons)
  • Inductive: Conclusion supported by premises to some degree

How do we evaluate arguments?
We have to ask ourselves the following questions:

  • How truthful are the reasons provided?
  • Is the structure of the argument valid?
  • Is the argument sound?

Let’s begin by answering the first question, “how true are the reasons being offered to support the conclusion?”

In order for us to evaluate this we must ask some further questions:

  • Does each reason make sense?
  • What evidence is there to ground these reasons?
  • From your experience have you seen this evidence to be true?
  • Are the sources of the evidence being provided trustworthy?

I would not fault you if you reflected on these questions and threw your hands up because, let’s face it: this is an ongoing process of analyzing and evaluating. There is, seemingly no end to the need for us to evaluate and analyze what is being presented to us.

Pardon me as I boldly declare that the enemies of the common good are in fact counting on you to not continuously evaluate and analyze what they are telling you.

“What,” you are probably wondering, “does it mean when I talk about a valid or invalid argument?”

An argument is defined as valid if the reasons presented support the conclusions in such a way that the conclusion follows from the reasons being provided.

An argument is described as invalid if the reasons do not support the conclusion and so the reasons do not lead us to draw the same conclusion presented.

Let’s consider the following invalid argument:
Reason: Yerkes National Primate Research Center refuses to stop experimenting on non-human primates.
Reason: The research being conducted at Yerkes is mediocre.
Conclusion: It is ethically wrong for Yerkes to experiment on non-human primates.

I may agree with the conclusion, I may agree with the reasons, but the reasons provided do not logically lead me to the conclusion.

What we are striving for in generating our arguments is that our arguments be sound. A sound argument is one that has both true reasons and a valid structure.

Chaffee provides us with this sound argument:
Reason: For a democracy to function most effectively, its citizens should be able to think critically about the important social and political issues.
Reason: Education plays a key role in developing critical thinking abilities.
Conclusion: Therefore, education plays a key role in ensuring that a democracy is functioning most effectively.
(Chaffee, The Philosopher’s Way, 22)

Click here to continue the lecture, where we will discuss the two categories of arguments.