Because

  How to Analyze and Evaluate Ordinary Reasoning

  Contradiction

 G. Randolph Mayes

 Department of Philosophy

 Sacramento State University

The Principle of Non-Contradiction

One of the most basic principles of logic is the Principle of Non-contradiction.  It is normally stated as follows:

  •  It is not possible for a statement to be true and false at the same time.

If we were to write this principle in the conditional form we are used to, it would read something like this:

  • If x is a statement, then x can not be both true and false at the same time.

Almost everyone understands the principle of non-contradiction at an intuitive level.  We simply do not go around saying things like:

  • Today is Monday and today is not Monday.

  • Rats are rodents and rats are not rodents.

  • Sam passed the class and Sam did not pass the class.

Nevertheless, there are times when we do commit ourselves to contradictory claims.  This occurs when we make statements that logically imply other statements that are themselves contradictory.  For example:

 

Example 1

Kate:  Look, I am overworked as it is, and I have absolutely no time to spend learning how to manage an entirely new filing system.  There was nothing wrong with the old one anyway.  If they were offering classes that would be different, but all they do is throw this manual at you and expect you to know how to do it by the end of the month!

 

Kate has said that she has absolutely no time to learn the new system and that it would be different if training classes were being offered.  But clearly training classes could only make a difference if Kate had time to take the classes, so Kate seems to be saying that she both has and does not have time to learn the new system.

 

Kate seems to have violated the principle of non-contradiction.  When we suspect someone has done this we may attribute to them the error of contradiction, which is defined as follows.

Contradiction

  • Definition:  Being logically committed to the truth of some  statement S and it's denial not-S at the same time.
  • MOI:  Identify the statement and show how what has been said involves a commitment to both the assertion and denial of that statement.

We would analyze Kate's case as follows:

Analysis

Kate is committed to the assertion and the denial of the following claim:  Kate has time to learn the new filing system.  Kate states explicitly that she does not have time to learn the new filing system.  But in saying that it would be different if they were offering training classes Kate implies that she does have time, since classes take time.

The main problem with accusing people of contradictions is that doing so often involves a violation of the principle of charity.  Because contradiction is such a fundamental error that almost everyone understands at an intuitive level, the principle of charity requires us to do our best to provide a logically consistent interpretation of what the person has said. 

In the case above, for example, it might have been more charitable to interpret Kate as meaning something more like this.

I have very little time to learn new things right now.  Learning a new filing system from a manual will take me a lot of time.  Training classes would take considerably less time, and I might be able to manage that.

Of course, this is not what Kate said, so this might be a little too charitable.

Example 2

Kevin:  I just found out that my best friend Frieda has been selling drugs to kids on the playground. I can't turn her in though.  I mean she is such a good person.  She wouldn't hurt a soul, and I can't bear the thought of her being in prison.

Analysis

Kevin is committed to the assertion and denial of the claim that Frieda is a good person.  He has explicitly asserted that Fried is a good person, but he has also said that Frieda sells drugs to kids, which is not something that good people ordinarily do.

Apparent contradictions

What makes things even more difficult is that people often choose to express themselves in a contradictory way.  This is because apparent contradictions get people's attention.  Phrases like "eight days a week" and "110% effort" are literally contradictory, but this is why people pay attention to them (for a while anyway). 

Advertisers exploit the appeal of contradictions as well.  Someone opening a run of the mill ice cream store might try calling it "the hottest ice cream in town".  Of course this is not literally contradictory.  Rather it simply equivocates on two different meanings of the term "hot."  Jokes like "I'd give my right arm to be ambidextrous" work in the same way.

The same thing goes on at the level of ordinary discourse.  If asked whether you want to go to a movie you might say:  I do and I don't.  Of course, all you mean by this is that you kind of want to go to the movie, but you kind of want to do something else, too. This is not a true contradiction, it is just an amusing (or annoying) way of talking.

Hypocricy

It's also important to know that the term "contradiction" is sometimes used to mean other things.  For example, hypocrites are people who "say one thing but do another."  They are often accused of being contradictory, but this is not a logical contradiction.  For example:

Selma:  I am an atheist, but I really think it's better if most people believe in God.  It's easier to be happy if you are simple-minded, and being afraid of God punishing you keeps you out of trouble as well.

Selma's statement may be both condescending and hypocritical, but it is not logically contradictory.  All Selma has said is that she does not believe in God but most people are better off if they do.