Detecting Assumptions in Arguments

Instructor: Jessica Mercado

I completed my BA in Criminal Justice in 2015. Currently working on my MS in Homeland Security Management.

This lesson covers how to determine if an argument has been made based off of assumptions. It will also cover what needs to be done in order to make an argument valid. Multiple examples of assumptive argruments are provided, along with their re-structured arguments.


You walk into your classroom feeling overly confident about your oral argument you will be presenting in class today. You stand in front of the class and begin your argument with this opening statement, ''Everyone knows that everyone likes mac and cheese.'' You provide no factual evidence that this is a true statement and you continue on by saying, ''Mac and cheese is a staple in all American homes.'' This statement was also not backed up by any facts. At the end of your argument, someone asks you where you got your information because he does not like mac and cheese. You are unable to provide an answer.

Did you make a valid argument?

Assumptions in Arguments

You just made a fallacious argument. But how so? Shouldn't everyone in the classroom agree with your argument? Since everyone has their own opinions and experiences, it should not be assumed that everyone understands and believes in the argument given. So, how do you go about identifying assumptions in an argument?

Two main steps can be taken in order to determine if assumptions are present or not. First, identify the validity of the sentence. If a sentence is valid, it will have facts or evidence to back up the argument. If it is not valid, no evidence or facts are given to back up the statements.

Lets take a look at our example again, ''Everyone knows everyone loves mac and cheese'', ''Mac and cheese is a staple in all American homes.'' Do these statements provide evidence or facts to back up their message? They do not, so these sentences are not valid.

Now the next step, you will ask yourself three questions:

  • What do these assumptions mean?
  • Why would the person presenting the argument accept the assumptions?
  • Should these assumptions be accepted?

''Everyone knows everyone loves mac and cheese.'' This statement means that there is no one that does not love mac and cheese. ''Mac and cheese is a staple in all American homes.'' This statement means that any home where mac and cheese is not a staple, they are not American.

Can Assumptions in Arguments be fixed?

You may accept these assumptions because you personally love mac and cheese, and in your home, mac and cheese is a staple. You do not know any different, so you assume that it is the same in every other American home.

Can these assumptions in your argument be fixed? You're in luck! It can be fixed! There are three different ways you can do so:

  • Provide background, facts, or evidence to support your claim.
  • Explain to your audience why they should agree with you. (Works on controversial or debatable topics).
  • Restructure the argument to not include assumptions. This can be done using general words such as: most, some, majority.

For the mac and cheese example, method three would work best. The new argument could be changed to the following:

''Most people find that mac and cheese is loved by a majority of people.''

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