Diagramming Arguments Congruent and Linked Arguments

An Argument An argument = a set of statements connected by a special relationship of justification; the statements provide evidence for the main claim

Independent Premises Falsity of one doesn’t cancel support the other provides.- independent proof. You shouldn’t buy a T.V. that costs over $300. This costs $450. It is also too big for your room. Don’t buy this T.V.

Dependent Premises Falsity of one can cancel support for others- interconnected. These premises cannot stand alone to provide proof.

Example of Dependent No floor with 2x4 joists on two foot centers is strong enough. This floor has 2x4 joists on two foot centers. So, this floor is not strong enough.

Convergent Arguments In convergent arguments, the premises provide different and independent reasons for the claim. Each can support the claim by itself.

Example-Convergent Nuclear power plants should not be built, because they are dangerous. And, the power from these plants is not essential. Finally, these plants are not fair to future generations.

Linked Arguments Linked argument- one in which the reasons are dependent on one another for their strength. They cannot stand alone.

Linked Argument There is reason to think the suspect is linked to this crime. The shots were fired from a jaguar; jaguars are not usual to this area; and the suspect owns a white jaguar.

Argument Diagramming Identify each claim and number them. Provide missing parts if needed. Determine relation of claims and diagram.

Persuade or Argue? Arguments seek to prove a point; to establish truth of a claim on basis of other claims. Persuasion seeks to win others to a point of view- may or may not have proof.

Is this an argument? “The desperate attempt by Hawks to link Iraq to the war on terrorism is based on blatant mis-information. Is there evidence?

Enthymemes-assumptions There can be implied or missing parts of an argument. Often it is assumed that you will supply the missing information or think it automatically.

What is missing? Jones will not win the election since his District is Democratic. You should prefer this tea as do professional tea- tasters.

What is missing? This film is too intellectual and thus probably will not be economically successful. Being a barber, you are no doubt a good conversationalist.

Common Assumptions Alice could not have been the robber, since Alice was not in Key West when the crime was committed/ At 10 a.m., August 9, she as in Miami.

Dubious Assumptions The Anacin difference-two standard aspirin tablets can 650 milligrams while two Anacin tablets contain 800 milligrams.- better?