Using Inductive Arguments

Inductive Arguments Move from specific examples or facts to a general conclusion Opposite of deduction (syllogisms) No distinctive form BUT there is a process to follow

Induction - Process 1) Decide on a question to be answered Or a tentative answer to a question (hypothesis) 2) Gather evidence 3) Move from evidence to conclusion by making an inference

Inference A statement about the unknown based on the known Answers the question Takes all evidence into account

Inductive process: example (557) 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

Inductive process (cont’d) Evidence: (cont’d) Some children were playing baseball this afternoon They were playing in the vacant lot across from the window. They stopped playing a little while ago. They aren’t in the vacant lot now.

Inductive process (cont’d) Conclusion: One of the children hit or threw the ball through the window; then, they all ran away.

Induction: Problems One additional piece of evidence can make the conclusion doubtful Ex: children were playing volleyball, not baseball Result? True answer can’t be inferred

Induction: Problems (cont’d) Even if conclusion is believable, you can’t necessarily assume it’s true The window could have broken some other way!

Induction: Problems (cont’d) What if the ball in the living-room had gone unnoticed all day? The second piece of evidence on the list would be untrue (conclusion is therefore unsound)

Induction: Problems (cont’d) Solution: Consider several possible conclusions Form multiple hypotheses and test each one Hypothesis: One of those children playing baseball broke the living room window. Hypothesis: A bird broke the window.

Induction: Problems (cont’d) If the gap between your evidence and conclusion is too great = jumping to a conclusion Hasty Not supported by the facts Essentially a premature inductive leap

Induction: Problems (cont’d) REMEMBER Hypothesis is just the starting point! Continue the inductive process as if the question were still to be answered (which it is)

Induction: Problems (cont’d) More evidence = smaller logical gap between evidence and conclusion Whatever the size of the gap, the crucial step between evidence and conclusion is called an inductive leap

Example of bad inductive leap Messenger: The Joan of Arc Story http://www.youtube.com/watch?v=ZtQEXW0lVts

Conclusion Inductive conclusions ARE NOT facts Facts = verifiable statements Inductive conclusions are inferences/opinions Never 100% certain At best, highly probable

Conclusion – Soundness? Not always easy to move from evidence you’ve collected to sound conclusion Gap REPEAT: More information = smaller inductive leap

Analysis of “A Scandal in Bohemia” The King of Bohemia hires Holmes to get compromising letters and a photograph from a former illicit lover, Irene Adler. As we read the end of this story together, try to figure out what type of reasoning is used by the characters!

Analysis of “A Scandal in Bohemia” Sherlock Holmes is a master of deductive reasoning Irene Adler, “the woman,” beats Holmes using inductive reasoning What a great twist! Rachel McAdams

Argumentation HW Patterns Argumentation Casebook Assignment: Casebook Assignment  Due 11/22 A Day and 11/23 B Day