Logical Fallacies

CSS 330-Critical Thinking and Computer Logic

Shelley Phumphrey

December 3, 2005

Logical fallacies are a part of everyday life. Many of us do not even realize their existence or means of use. A logical fallacy is faulty reasoning to an argument that is not only wrong, but sounds so convincing that a number of people who hear it are fooled by this reasoning and believe it to be true. Many times people mistake logical fallacies with critical thinking and incorporate these fallacies into their decision making process unintentionally. The three fallacies that will be detailed are slippery slope, hasty generalization and questionable cause. The first logical fallacy is the slippery slope. The slippery slope claims that a relatively harmless act if left unchecked will eventually lead to a disastrous event or once one step is approved this will lead to a chain of events. The reasoning is based on insufficient evidence that one action will lead to another. A group will start the decision making process on a relatively easy problem. However, as the group discusses this problem one step leads to another and by the end of the decision making process, the group is trying to avert a disaster. People tend to make more out the problem then there is. The group fixes the relatively simple problem and some time later decide to take the solution to the next step. If fixing the minor problem were good, then correcting a bigger scope problem would be even better. The group gets back together and decides to enlarge their scope even more and correct what they perceive to be an even larger problem. Based on the groups critical thinking, it was determined that correcting each succession of problems would make the world a much better place, when in fact the group has angered many others with their strict policies. This example of slippery slope was taken from the trial Tennessee vs Scope (MacLachlan, 1997). The main premise of the trial was the legality of teaching evolution in the schools. On the second day of the trial the following slippery slope example was delivered in court. The courts can rule that is illegal to teach the theory of evolution in public schools and then in a few days, the courts can rule that is illegal to teach evolution in private schools. Then after a year has passed, the courts may decide it is illegal to teach evolution in religious schools. As can be seen in this example, if the first step can happen then it is thought the second step will happen and so forth. This line of thought was used to convince people that they would lose some freedoms based on the logical fallacy presented in court.

The second logical fallacy is the hasty generalization. Hasty generalization is basing a solution or decision on a group that is biased or to small. The key to making a decision involving the opinion of a group of people is using an unbiased group or a group that is large enough to reflect the general populace ideals. A company has a problem to solve and begins the decision making process. The options are presented and the company decides to use the opinions of five people off the street to decide if the company's product is better then their competitors. Based on the company's proper critical thinking, but poor decision-making, they decided on an option without putting sufficient research on the proper sampling size. The five people chosen may all like the company's product or all may hate it. The sampling size is too small and biased to make a proper decision. The first example was taken from Edwards (2000). A reader wrote in stating that she needed to start thinking about retirement homes for her mother, who was 58 years old. The writer had the belief that as a person approached the age of 60 that he or she needed to be placed in a nursing home. The writer made a hasty generalization that all people needed to be placed in a nursing home when they reached 60 years old. The writer should have researched a larger group of older people to determine what additional factors needed to be considered and what age should a person start considering a nursing home. There are many people who are leading productive lives in their 80s and 90s. The second example is taken from Wheeler (1976). The Literary Digest polled approximately two million people before the 1936 presidential election. Based on the results, the Digest stated that Republican Alf Landon would win the election. However, President Roosevelt won by a decisive margin. Even though the Digest used a large polling group, the group was made up mostly of wealthy Americans. During the 1930s, the majority of wealthy Americans were Republican,