Formulating an Argument Part One: Inductive and Deductive Reasoning

Induction From the Purdue OWL handout: Induction is the type of reasoning that moves from specific facts to a general conclusion. When you use induction in your paper, you will state your thesis (which is actually the conclusion you have come to after looking at all the facts) and then support your thesis with the facts.

Example From the Purdue OWL handout: Conclusion: Jones killed Smith Support: Smith was shot by Jones’ gun, Jones was seen entering the scene of the crime, Jones and Smith argued earlier in the day Smith died. Assumption: The facts are representative, not isolated incidents, and thus reveal a trend, justifying the conclusion drawn.

Discussion Assumption: The facts are representative, not isolated incidents, and thus reveal a trend, justifying the conclusion drawn. What does it mean for a facts to be “representative, not isolated incidents”?

Induction Inductive reasoning is often called a “bottom up” approach. This is a metaphor that expresses the idea that specific, real-world observations and the patterns they can lead to are “lower” than the hypotheses and theories that we then arrive at.

http://www. livescience. com/21569-deduction-vs-induction http://www.livescience.com/21569-deduction-vs-induction.html "In inductive inference, we go from the specific to the general. We make many observations, discern a pattern, make a generalization, and infer an explanation or a theory,"

Induction The bottom up approach means we start at the bottom with observations and work toward the top: Theory Hypothesis/Generalization Pattern/trend Obervations

Faulty Induction We have to be careful not to over-generalize. Induction is probabilistic, not deterministic. “Even if all of the premises are true in a statement, inductive reasoning allows for the conclusion to be false.” (livescience.com)

Faulty Induction: Examples http://www.businessdictionary.com/definition/inductive- reasoning.html "All cats have four legs; my dog has four legs; therefore my dog is a cat."

Faulty Induction: Examples Tim is Canadian. Tim has no hair. Canadians have no hair.

Faulty Induction: Examples A man jumps out a window on the 100th floor of a skyscraper. As he passes the 99th floor window, he thinks, “So far, so good!” He passes the 98th floor window, and thinks, “Everything is fine!” This continues as he falls. As he passes the 1st floor window he uses inductive reasoning to conclude that jumping out a window on the 100th floor of a skyscraper is perfectly safe. After all, he has passed 98 floors without any problem at all!

Deductive Reasoning Deduction is a “top down” approach: Theory Hypothesis/Generalization Pattern/trend Obervations "In deductive inference, we hold a theory and based on it we make a prediction of its consequences. That is, we predict what the observations should be if the theory were correct.” (livescience.com)

Deduction: Example Syllogistic reasoning: (see the OWL handout) Major premise Minor premise Conclusion A very famous example: All men are mortal. Socrates is a man. Therefore, Socrates is mortal.

Deduction Deduction, done properly, is not probabilistic. It is interesting, though, that the major premise “all men are mortal” is actually inductive! We arrive at this premise because of the observation that billions upon billions of humans have died, and none (that we know of!) are immortal.

Faulty Deduction In order for deduction to work, the reader has to agree with the premises (remember hedging!). See the OWL handout for the example about Lincoln.

Faulty Deduction If one or more of the premises is incorrect, the whole argument falls apart: A common logical fallacy is called “begging the question”. This means that we start with a premise that we assume is true, but which hasn’t actually been proven

Faulty Deduction In the OWL handout, we see: All dogs make good pets. Doogle is a dog. [Therefore], Doogle will make a good pet. Clearly, this begs the question, because we’re starting from an assumption that is not necessarily true, or has not been shown to be true.

Faulty Deduction Another famous example of begging the question is: “When did you stop beating your child?” This question assumes that you beat your child, but that has not been established yet!

More logical fallacies: https://owl.english.purdue.edu/owl/resource/659/03/ https://quizlet.com/98111145/logical-fallacies-faulty-deduction-flash- cards/ https://knowledgeguild.wordpress.com/2014/02/28/faulty-deduction/