Matters of Life and Death

Fall 2004


The point of an argument is to give good reasons for accepting a claim (the conclusion).  An argument is something stronger and more persuasive than a mere opinion.  What makes an argument persuasive is that it makes its assumptions (premises) clear and then shows how these assumption lead logically to the conclusion.

Good papers make arguments.  The thesis is a statement of the conclusion of the argument, and the paper provides and explains the premises needed to reach this conclusion.

Some examples of arguments:

  1. All cats are mammals.  (premise)
  2. Bucky is a cat.  (premise)

Thus, Bucky is a mammal.  (conclusion)

  1. Once I know someone has lied to me, I just can't trust him.  (premise)
  2. My dad once told me that the toothfairy exists.  (premise)
  3. Later, I found out that the toothfairy didn't exist.  (premise)
  4. So, I know that my dad lied to me about the toothfairy.  (conclusion from 2 and 3)

Therefore, I can't trust my dad.  (conclusion from 1 and 4)

  1. Britney Spears is from Mars.  (premise)
  2. Martians have astounding vocal range and are great dancers.  (premise)

Hence, Britney Spears has astounding vocal range and is a great dancer.

Evaluating arguments

Authors aspire to build valid arguments.  These are arguments in which the truth of the premises guarantees the truth of the conclusion.  If one's audience recognizes an argument as valid [1] , and also accepts the premises as true, it must also accept the conclusion as true. 

There are many valid arguments which are not persuasive, however, because their audience rejects one or more of the premises on which they rest.  A sound argument is one which is valid and all of whose premises are true.  In some cases, it may be easy to determine whether a premise is true or false (e.g., if the premise makes a claim about a matter of fact which can be checked -- that the Yankees won the 1989 World Series [2] , or that only mammals have hair [3] ).  In other cases, arguments may rely on premises about matters of fact which are much harder to verify -- e.g., that God exists, that time and space are illusions.  Sometimes the best one can do is to show such premises to be probable, or at least more probable than an alternative.  Other times, one may rely on these premises because they are appealing ones to the target audience for the argument, whether or not the premises can be shown decisively to be true.

There are two basic ways to take issue with an argument.  One is to point out a flaw with its logical structure (that is, to show that the conclusion doesn't follow from the premises.  Another is to point out a problem with the premises.

Logical flaws:

Each of the following arguments rests on faulty logic:

  1. If my battery is dead, my car won't start.
  2. My car doesn't start.

Thus, my battery must be dead.

(Problem:  1 and 2 don't necessitate the conclusion; there are plenty of other reasons my car might not be starting besides a dead battery.)

  1. Only ducks quack.
  2. This bird doesn't quack.

So, it's not a duck.

(It might just be a very quiet duck!)

1.     If you eat tainted crab, you'll get food poisoning. 

  1. That crab you ate was not tainted. 

Therefore, you won't get food poisoning. 

(The crab may have been OK, but the raw egg on your Caesar salad was loaded with salmonella.)

When evaluating someone else's argument (or your own), check to be sure the pattern of reasoning doesn't make one of these mistakes.  If it does, it's a bad argument. [4]

False premises:

Another good reason to reject an argument is that you can demonstrate that it rests upon bad assumptions.  Sometimes this is easy (as when the argument assumes that Britney Spears is from Mars and we can produce the birth certificate showing she was born on Earth).  Other times, you can question premises because they rest on common fallacies. 

Here are some common fallacies that base arguments on highly suspect premises.  Note that the conclusion to an argument committing one of these fallacies may still be true, but these are not good ways to get someone to see that it's true!

      Circular reasoning:  assuming what you say you're proving.  Usually the "identical" premise and conclusion are expressed with slightly different words.

      False dilemma:  claiming that one of two alternatives must be true while ignoring other possibilities.  (Everyone here is pre-med or pre-law.)

      Slippery slope:  introducing a questionable conditional (if-then) claim.  (If we decriminalize drugs, then everyone will become a drug addict.)

      False analogy:  basing an argument on a claim that two things are similar in a way that has particular consequences, when really the two things are not similar in that way, or being similar in that way does not really have the claimed consequences.  (The world is like a watch in its highly ordered structure of interconnected parts.  Thus, like a watch, the world must be the product of intelligent design. [5] )

      Post hoc:  inferring that, because one event came before a later event, it caused that later event.  (I started sneezing right after Jerry Springer's face came on the screen.  Seeing him must make my sinuses go crazy.)

You may also disagree with an argument because it rests on assumptions that you suspect are wrong.  If you can't prove these assumption false outright, you can still offer reasons why they're not reasonable assumptions, or reasons why a different assumption seems more reasonable.

Keeping the discussion to the merits of the argument:

When you're responding to an argument someone else has made, or offering an alternative to that argument, there are a couple of ways you should never treat your opponent:

      Ad hominem:  attacking your opponent's character rather than dealing with the substance of her claims (i.e., whether her premises are true or probable, whether her conclusion follows logically from her premises).

      Straw man:  attributing a position to your opponent that he doesn't actually hold.  This position is usually one that is easier to defeat than his actual position.

[1] There may be valid arguments, however, which are so long, convoluted, or badly presented that they are not recognized as valid by the reader.  Here, you are faced with a double-standard:  As a student reading difficult texts, it is your job to dig out the structure of arguments despite confusing presentation, and to presume an argument is valid until you've proven otherwise.  As a student writing papers, however, it is your job to present arguments to your reader clearly, so he can recognize their validity; otherwise, you will fail to persuade that reader.

[2] They didn't.

[3] They do.

[4] Using a flawed pattern of reasoning makes the argument bad even if the conclusion is true!  Why?  It's bad because the argument is not giving good reasons to support that conclusion.

[5] How closely does the world really resemble a watch?  It doesn't have gears, hands, a battery, a luminescent face, etc.  Also, is intelligent design the only thing that can produce a highly ordered structure of interconnected parts?


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