Inductive & Deductive Logic Kirszner & Mandell White and Billings

Deductive Reasoning Deductive Reasoning proceeds from a general premise or assumption to a specific conclusion –If all statements in the argument are true then the conclusion must also be true

Deduction Syllogism –Major Premise (general statement) –Minor Premise (more specific statement) –Conclusion (drawn from premise)

Examples of Syllogism Jesse Owens All Olympic runners are fast Jesse Owens was an Olympic runner Therefore, Jesse Owens was fast Declaration of Independence –Tyrannical Rulers deserve no loyalty –King George III is a tyrannical ruler –Therefore, King George III deserves no loyalty

Illogical Syllogisms Dogs and Cats –All dogs are animals –All cats are animals –Therefore, all dogs are cats Ralph and the Dog –All dogs are animals –Ralph is an animal –Therefore, Ralph is a dog Problems Two major premises Undistributed vs. Distributed (some items) vs. (all items) The minor premise must refer to the term in the major premise that is distributed.

Deduction Valid Argument – when conclusion follows logically from major and minor premises. If your audience accepts your major and minor premise then they will be more likely to accept your conclusion.

Deductive Practice Try to write a syllogism for your argument that you are thinking about covering in you research paper. Write it on a blank piece of paper with your name in the top right corner. Trade w/ the opposite gender Trade w/ someone with similar hair Trade w/ someone who you don’t trade with

Inductive Reasoning Inductive Reasoning proceeds from individual observations to a more general conclusion and uses no strict form. –All relevant evidence be stated and that the conclusion fit the evidence better than any other conclusion.

Inductive First you decide on a question to be answered, or a hypothesis Second – Gather evidence Third – move from evidence to conclusion by way of inference

Inductive –Question: How did that living-room window get broken? –Evidence: There is a baseball on the living room floor. The baseball was not there this morning. Some children were playing baseball this afternoon. They were playing in a vacant lot across from the window. They stopped playing a little while ago. They aren’t in the vacant lot now. –Conclusion: One of the children hit or threw the ball through the window; then, they all ran away.

Inductive Practice Try to write a hypothesis or Question for your research paper then list some of the evidence you need to uncover in order to prove your hypothesis Write this on the opposite side of your Syllogism Trade with three other people – try to find holes in the evidence or alternate conclusions –(i.e. what about …? OR Did you consider …?)