Logical Arguments

Learning Objectives

  • Identify logical structures in argument

Anything you read that includes an attempt to persuade you to think a certain way is likely to include logical argument as part of that persuasion.

The text below introduces the idea of premises and conclusions. As you view this, think about the relationship of premises and conclusions as they align with main ideas and supporting evidence in paragraphs that we explored earlier in this module.

Elements of an Argument

Argumentation Vocabulary

Claim: a statement or opinion that is either true or false

Argument: a claim supported by premises

Conclusion: the main claim in an argument

Premises: claims that support and argument’s conclusion

A claim is an assertion about the truth, existence, or value of something that is either true or false. Claims are also called statements or propositions.

When supported by premises, a claim becomes a conclusion. For example:

  • This class is easy.
  • The Detroit Lions have the potential to make the NFL playoffs.
  • This chemical structure is unstable.
  • Democratic socialism is superior to a pure democracy.

An argument is an assertion that contains both a conclusion and premises. It is a statement of fact or opinion that is based on evidence. Keep in mind that not all statements are arguments, and some statements may contain multiple arguments.

Test It Out

Which of the following statements is an argument?

  1. Vending machines stocked with soda or candy should be removed from all public schools.
  2. Star Wars is the best movie ever.
  3. We’d better leave now. If we don’t, we might miss the last train and we’ll be stuck here all night.

A conclusion is the main claim of an argument that is supported by a premise. It is the logical result of the relationship between the premises. Identifying the conclusion is the first step in understanding the argument.

But how do you identify the conclusion? Follow these steps:

  1. Ask, “Is the statement the main point, or is it a claim given to support another statement in the argument?
  2. Identify the indicator word that often precedes the conclusion, such as
Therefore Thus As a result That’s why Consequently So
This Means This shows It follows that This suggests Hence Accordingly

Test It Out

What is the conclusion in each of the following arguments?

  1. Abortion is wrong because all human life is sacred.
  2. It’s flu season and you work with kids, so you should get a flu shot.
  3. We should believe that rocks exist because we are able to see them.
  4. John will probably receive the next promotion since he’s been here the longest.
  5. We must reduce the amount of money we spend on space exploration. Right now, the enemy is launching massive military buildup, and we need additional money to purchase military equipment to help match the anticipated increase in the enemy’s strength.
  6. It’s a beautiful day. We should go to the park. Besides, I need some exercise.
  7. That movie has had horrible reviews. My sister saw it and said it was boring and her friend spotted three mistakes. Pick a different movie. I am sure we can find something better.

A premise is a reason offered as support, or evidence, for another claim. It is often indicated by these words:

Because For As
Since Inasmuch as As shown by
Given that As indicated by The reason is that

Consider the following statement: Today’s freshmen cannot write very well. Joe is a freshman, so he must be a poor writer. The premises and conclusion are identified as follows:

Premise Today’s freshmen cannot write very well
Premise Joe is a freshman,
Conclusion so he must be a poor writer.

Practice identifying the premises and conclusions

In order to identify the premises and conclusion, you should first rewrite the argument in standard form. You do this by identifying which claim is the conclusion, then working backwards to identify which claims are premises that support the conclusion. It should look like this:

Standard Form
Premise 1:
Premise 2:
Conclusion:

Practice in the following presentation: