A photograph of a male student lying in the grass and reading a spiral bound text.

Source: Student studying on the lawn, UBC Library, Flickr

Now that you have learned about inductive and deductive reasoning and logical fallacies, you will analyze an argument to determine the effectiveness of the writer’s reasoning and evidence. In evaluating an argument, think of yourself as a member of a jury who must weigh the evidence and come to a verdict. In doing so, you will consider not only the reasoning process and the presence or absence of logical fallacies, but also two other important elements of a sound argument: definition of terms and the willingness of the writer to acknowledge other points of view.

A photograph of a female attorney presenting an argument.

Source: Spohrer Dodd Trial competition 2009, CoastalLaw, Flickr

The “case” before you is this: “Should dogs be allowed in state and national parks?” You will hear from both sides and then make a “yea” or “nay” decision. The bases for both arguments are taken from Seth Trigg’s opinion, which is expressed in his blog titled “Should Dogs Be Allowed in Public Parks?” After you have completed a first reading of each argument, you will be prompted to return to each one to weigh the evidence in several ways.

A photograph of a male lawyer arguing a case before a jury in a court room

Source: Nathan-present-opening-MS, Rosie O’Beirne, Flickr

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A photograph of a children's jury in a courtroom

Source: Courtroom Drama, Erin Nealy, Flickr

Now, weigh the evidence in Argument 1. Starting with the second sentence, decide whether the text is (1) the writer’s perspective (opinion) and conclusion, (2) a reason for the writer's claim, (3) evidence used to back up the writer's reasons, or (4) acknowledgment of the opposing argument.

For the writer's perspective and conclusion, you might ask yourself the following:

To identify reasons the writer offers in support of his claim, you might ask these questions:

To identify evidence that the writer offers to back up his reasons, you might ask the following:

A photograph of a several young people sitting a table presenting or arguing a topic with documents and books spread out before them

Source: SLIs 2011, SenJeffBingaman, Flickr

To identify an opposing argument acknowledged by the writer, you might ask this question:

Now, return to Argument 1 above and identify the elements of the argument. Click on the second sentence to begin identifying these elements. Make your choices from the pull-down menu. When you are finished, read the second article. Then, weigh the evidence in Argument 2 by identifying the elements using these same instructions.

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A photograph of a group of students at a conference sitting in a circle looking at various printed literature and having a discussion.

Source: SLIs 2011, SenJeffBingaman, Flickr

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Let’s now compare the overall effectiveness of the two arguments. To evaluate them, ask yourself these three questions. Use your notes to write your answers. When you are finished, check your understanding to see possible answers.

  1. Which argument included a slippery slope logical fallacy? What was it?
  2. Which argument committed the ad hominem fallacy rather than respectfully acknowledging other points of view?
  3. Did either argument define terms, such as “responsible pet owners”?
Check Your Understanding
Sample Responses:
  1. You should have recognized the slippery slope fallacy in Argument 2: “If dogs are banned in state and national parks, next, children under the age of 5 will not be permitted, and then children under the age of 16, and then you’ll have to be 21 to enter a public park.”
  2. Argument 2 is guilty again: “People who don’t want to allow dogs in public parks are not real Americans.” The attack on possible opponents to the writer’s argument decreases the effectiveness of her claims and makes the arguer seem unreasonable.
  3. Neither argument clearly defined a responsible pet owner. Argument 1 hinted at the idea by suggesting that responsible pet owners would keep their dogs leashed.

The verdict may never be in on the issue of allowing dogs in state and national parks, but Argument 1 includes more detailed evidence to support its premises, and it is free of logical fallacies.