Copyright

Affirming the Consequent Fallacy: Definition & Examples Video

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Free Will: Determinism, Compatibilism & Libertarianism

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:02 Up All Night
  • 0:43 Conditionals & Consequents
  • 1:36 Affirming the Consequent
  • 3:41 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Timeline
Autoplay
Autoplay
Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Christine Serva

Christine is an instructional designer, educator, and writer with a particular interest in the social sciences and American studies.

Learn how to draw better conclusions by exploring the flaws in the affirming the consequent fallacy. You will be able to spot this problem even when the argument sounds logical.

Up All Night

Carla is very sensitive to caffeine. One cup of coffee in the evening and she'll be up all night long, unable to sleep. She always orders caffeine-free tea and soda. Plenty of times, she's ordered a caffeine-free drink and found herself jittery and lying awake in bed. When this happens, she concludes, 'They got my order wrong. It must be the caffeine keeping me up.'

In this lesson, we'll look at Carla's conclusion and consider whether she has reason to believe what she does about why she's up all night. We'll focus on the affirming the consequent fallacy and how to avoid confusing it with logic that is correctly used.

Conditionals and Consequents

Here's how Carla began her argument. She said, 'If I have caffeine in the evening, then I'm awake all night.' The format of her sentence is known as a conditional statement, an if-then statement which includes two parts: an antecedent and a consequent. The antecedent is the 'if' part of a conditional statement, and the consequent is the 'then' part of a conditional statement. Sometimes 'then' won't be used in the sentence, but the format is still basically 'If A is true, then C is true.'

There's nothing faulty in saying the statement that if she has caffeine, she'll be up all night. But then Carla goes on to say, 'I'm awake all night. Therefore, I must have had caffeine this evening.'

What's wrong with her logic? She's awake all night, so that's simply a fact she's reporting. Can Carla reasonably conclude that this means someone gave her a caffeinated beverage by mistake?

Affirming the Consequent

When Carla says, 'I'm awake all night,' she affirms the consequent has happened. She's awake. The fallacy of affirming the consequent occurs when a person draws a conclusion that if the consequent is true, then the antecedent must also be true.

Written in letters where the antecedent is represented by A, and the consequent is C, this argument looks like this: 'If A, then C.' 'C, therefore, A.' 'If I have caffeine' (antecedent), 'I will be awake all night' (consequent). 'I'm awake all night' (consequent). 'Therefore, I must have had caffeine' (affirms the consequent, concluding that the antecedent must have occurred).

This is not to be confused with the logical argument a person could make that goes like this: 'If I have caffeine' (antecedent), 'I will be awake all night' (consequent). 'I had caffeine. I will be awake all night.' In this case, it's okay to affirm the antecedent and then affirm that the consequent will then be true. This is because an if-then statement is designed to describe just such situations and gives you a logical argument to use. The problem is when the reverse occurs. Then a faulty conclusion could be made.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account
Support