How to Argue Successfully Deductive and Inductive Reasoning

Introduction “Logic has been a formal academic discipline for almost 2,500 years. For much of western history, logic was one of the main branches of schooling (the classical curriculum consisted of grammar, logic and rhetoric - Language used to persuade or influence others). With the growth of more specialized disciplines and wider curricula in the 20th century, formal logic got lost in the shuffle. In its place, philosophers began formulating courses in what we now call critical thinking, or informal logic.” (FactCheckEd.org, 2008)

Definitions Argument: a conclusion together with the premises that support it Premise: a reason offered as support for another claim Conclusion: the claim being supported by a premise or premises

Definitions Continued Valid: an argument whose premises genuinely support its conclusion Unsound: an argument that has at least one false premise Deductive: an argument whose premises make its conclusion certain Inductive: an argument whose premises make its conclusion likely

Inductive Reasoning When detectives arrive at the scene of a crime, the first thing they do is look for clues that can help them piece together what happened. A broken window, for example might suggest how a burglar entered or exited a house that had been robbed. This process is called inductive reasoning. It consists of making observations and then drawing conclusions based on those observations. Using inductive reasoning generally involves the following questions: 1. What have you observed? 2. What evidence is available? 3. What can you conclude from that evidence? 4. Is that conclusion logical? Example: You might notice that every time you eat a hot dog with chili and onions, you get a stomachache. Using inductive reasoning, it is likely that chili dogs cause you to have indigestion and you should probably stop eating them.

Inductive Reasoning Example Example: You might notice that every time you eat a hot dog with chili and onions, you get a stomachache. Using inductive reasoning, it is likely that chili dogs cause you to have indigestion and you should probably stop eating them.

Deductive Reasoning The difference between an inductive and deductive argument is that in an inductive argument the conclusion is likely. In a deductive argument the conclusion is certain. The premises (clues) in a deductive argument guarantee the truth of the conclusion. Example: Smith owns only blue and brown pants. Smith is wearing a pair of his pants today. (Premise) So Smith is wearing either blue or brown pants today. (Conclusion)

Example Valid Deductive Reasoning All German Shepherds are dogs. - Argument Some pets are German Shepherds. - Premise Therefore, some pets are dogs. - Conclusion * Invalid Deductive Reasoning

Practice Is the following an example of inductive or deductive reasoning? 1.The soccer game is on either Thursday or Friday. I just found out that the game is not on Thursday, so the game must be on Friday. 2.January has always been cold in Siberia. Today is January 14 th, so it is going to be another cold day in Siberia.