Introduction to Argumentation Keen Forms of Reasoning Deduction

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Introduction to Argumentation Keen
Forms of Reasoning
Deduction: going from something we know for a fact to a conclusion about something else. This can be expressed in a syllogism.

A syllogism has three parts: major premise, a minor premise, and a conclusion

All men are mortal.

Socrates is a man.

Socrates is mortal. A good president has some foreign policy experience.

George W. Bush has no foreign policy experience.

George W. Bush will not be a good President.
College graduates usually get better-paying jobs than high school graduates.

Smith wants a high salary.

Smith should go to college.
Induction: the process of observing facts until we perceive some kind of relation between them that allows a conclusion to be drawn.
Inductive reasoning is often used in medicine: e.g., non-smokers who live with smokers have higher rates of cancer and lung disease than nonsmokers who live with nonsmokers.
Induction draws on experience and requires you to collect facts and attempt to make sense of them. You can draw the wrong inference from observable facts.

Kinds of Argument

Argument by Authority

Harold Bloom says that Shelley is a better poet than Keats.

Argument by Analogy: a comparison of two essentially unlike things
FDR said that giving guns and ships to the British was just like a neighbor loaning a fire hose when a neighbor’s house is on fire.
a fortieri (to the stronger): an argument that proceeds by saying that “if we know A is true, then it’s even more likely that B will be true.”
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  1. Post hoc ergo propter hoc fallacy (after this, therefore because of this).

  2. Straw man argument. An argument with something you claim your opponents are saying, when in fact they are not saying it at all; or, an argument with an opponent who is especially weak, chosen instead of strong opponents.

  3. Ad hominem. Attacking the person. (This can be a legitimate argument.)

  4. Either/or fallacy. “Anyone who liked that movie is either a lunatic or a sadist.”

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