Intro to Logic: Recognizing Arguments

by Luke Muehlhauser on June 23, 2009 in Intro to Logic

Welcome to my course Intro to Logic (index). Here, we learn the basic skills of good thinking and their benefits in real life.

Last time, I discussed the building blocks of arguments, propositions. Now we are going to learn how to recognize arguments.1

An argument presents premises in support of a conclusion, like this:

  1. All men are mortal.
  2. Socrates is a man.
  3. Therefore, Socrates is mortal.

But most arguments are not presented so clearly. These examples should give you an idea of the variety of forms in which arguments come:

  1. A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed. (The Constitution of the United States)
  2. Forbear to judge, for we are sinners all. (Henry VI, William Shakespeare)
  3. He that loveth not knoweth not God, for God is love. (1 John 4:8)
  4. Archimedes will be remembered when Aeschylus is forgotten, because languages die and mathematical ideas do not. (A Mathematician’s Apology, G.H. Hardy)
  5. Why decry the wealth gap? First, inequality is correlated with political instability. Second, inequality is correlated with violent crime. Third, economic inequality is correlated with reduced life expectancy. A fourth reason? Simple justice. There is no moral justification for chief executives being paid hundreds of times more than ordinary employees. (“When the Rich Get Even Richer”, Richard Hutchinsons)
  6. Dude, let’s go to Wendy’s. They have the Jr. Bacon Cheeseburger there, and it tastes like a fried slice of Megan Fox’s ass. (me, yesterday)

Of course, we’ll have to do some generous paraphrasing to put these arguments into a form we can analyze, but there’s no doubt they were meant as arguments. Let’s consider the last one. We might break this down as:

  1. We should eat at a place that offers tasty food.
  2. A fried slice of Megan Fox’s ass would be tasty food.
  3. The Jr. Bacon Cheeseburger tastes like a fried slice of Megan Fox’s ass.
  4. Wendy’s offers the Jr. Bacon Cheeseburger.
  5. Therefore, we should eat at Wendy’s.

A compelling argument, don’t you think? We went to Wendy’s.

Finding arguments

Here’s a list of words and phrases you’ll often find right next to the conclusion of an argument. Look for them and you’ll probably spot an argument:

  • therefore
  • hence
  • thus
  • so
  • for these reasons
  • it follows that
  • we may infer
  • I conclude that
  • which shows that
  • which entails that
  • which implies that
  • consequently
  • proves that
  • as a result
  • for this reason

There are also certain words and phrases that usually accompany a premise in an argument:

  • because
  • since
  • for
  • as
  • the reason is that
  • as indicated by
  • follows from
  • as shown by
  • inasmuch as
  • in view of the fact that
  • may be inferred from

But these words and phrases alone won’t catch all arguments, for example this one:

Whether or not to smoke is a conscious decision, made in the light of an abundance of information on the lethal effects of tobacco. Surely those who choose unwisely should bear the cost of any resulting ill health.2

And sometimes a premise is not given in declarative form, but as rhetorical question:

If a man say, ‘I love God,’ and he hateth his brother, he is a liar; for he that loves not his brother whom he hath seen, how can he love God whom he hath not seen? (1 John 4:20)

Or, the conclusion is given as a command:

Wisdom is the principal thing; therefore get wisdom.

Which of course can be interpreted as:

  1. Wisdom is the principal thing.
  2. Therefore, one ought to acquire wisdom.

Missing premises

Many arguments assume certain premises that are not stated, as in my Jr. Bacon Cheeseburger argument given above. Such arguments are called enthymemes (but there won’t be a test on that). Here’s another example, from Shakespeare’s Julius Caesar:

He would not take the crown;
Therefore ’tis certain he was not ambitious.

This argument depends on a missing premise, that “One who would not accept the crown must not have been ambitious.”

Arguments and explanations

It can be easy to mistake explanations for arguments, since explanations also use words like “because” and “therefore.” Consider:

Therefore is the name of the tower called Babel, because the Lord did there confound the language of all the earth. (Genesis 11:9)

This sentence does not assert a conclusion supported by premises. Rather, it gives an explanation. It explains why the tower was called Babel. Of course, this explanation could be asserted as a conclusion or a premise in another argument. Perhaps it is not true that this is why the tower is called Babel. But this sentence by itself does not contain an argument.

But sometimes, a genuine argument looks like an explanation:

Ellen R. Fox’s complaint – that you noted that Catherine Deneuve was “perhaps not as slender as she once was” but that you did not mention Donald Trump’s growing girth – is easily explained. Mr. Trump never appeared nude in a movie that made his shape a matter of interest.3

Though it uses the word “explained,” this is an argument, one we might paraphrase like so:

  1. Nude appearance in a movie makes one’s appearance a matter of interest.
  2. Mr. Trump never made a nude appearance in a movie.
  3. Ms. Deneuve did make a nude appearance in a movie.
  4. Therefore, Mr. Trump’s appearance is not a matter of interest, but Ms. Deneuve’s appearance is a matter of interest.
  5. It is appropriate for a newspaper to comment on the appearance of a prominent person if their appearance is a matter of interest.
  6. Therefore, it was appropriate for this newspaper to comment on the appearance of Ms. Deneuve without commenting on the appearance of Mr. Trump.

Now that we are equipped to recognize arguments when they appear, we will start to see how to sift bad arguments from good ones in the next post.

(Also see the post index to this Intro to Logic series.)

  1. My examples are drawn from the 11th edition of Copi & Cohen’s excellent Introduction to Logic. []
  2. “Is Smoking a Choice?”, Lois Taylor []
  3. Andy Rooney in the New York Times on April 29, 1996. []

Previous post:

Next post:

{ 2 comments… read them below or add one }

Reginald Selkirk June 24, 2009 at 10:25 am

If a man say, ‘I love God,’ and he hateth his brother, he is a liar; for he that loves not his brother whom he hath seen, how can he love God whom he hath not seen? (1 John 4:20)

Luke 14:26 If any man come to me, and hate not his father, and mother, and wife, and children, and brethren, and sisters, yea, and his own life also, he cannot be my disciple.

  (Quote)

Kip June 24, 2009 at 10:51 am

Reginald Selkirk: Luke 14:26 If any man come to me, and hate not his father, and mother, and wife, and children, and brethren, and sisters, yea, and his own life also, he cannot be my disciple.

Clearly you can either a) love God, or b) be a disciple of Jesus, but not both(*).  :-)
We’ve just created another argument!
(*) “neither” is also an option, of course.

  (Quote)

Leave a Comment