1. Logıcal structures of arguments

2. An Overview of Logos
Logos refers to the strength of an argument’s support and its internal consistency.
Logos is the argument’s logical structure.
But what do we mean by “logical structure”?

3. Formal Logic versus Real-World Logic
Logical structure in our case does not mean the formal logic in philosophy.
A is B; B is C; so A is C
This logic may not be true in the real world
So, using the word prove in claims is not a good way (e.g.This paper will prove that euthanasia is wrong).
Real-world arguments seldom prove anything.
They can only make a good case for something, a case that is more or less strong, more or less probable.
You may strengthen the determination of those who agree with you or weaken the resistance of those who oppose you.

4. The Role of Assumption
Two basic differences between a formal logic and real-world argument:
Real-world arguments are not grounded in universal statements: They are grounded in beliefs, assumptions and values
These beliefs, assumptions and values in real-world arguments are often unstated
Then an argument is persuasive if the audience agrees with you
If they don’t, the writer should defend the assumption

5. The Core of an Argument: The Enthymeme
Enthymeme means in mind: Listeners or readers must have in mind an assumption, belief, or value that lets them willingly supply the missing premise.
If the audience is unwilling to supply the missing premise, then the argument fails.
i.e., Successful arguments depend both on what the arguer says and on what the audience already has “in mind.”

6. Claims are supported with reasons
Claims are supported with reasons. You can usually state a reason as a because clause attached to a claim.

7. A because clause attached to a claim is an incomplete logical structure called an enthymeme. To create a complete logical structure from an enthymeme, the underlying assumption (or assumptions) must be articulated (stated directly).

8. To serve as an effective starting point for the argument, this underlying assumption should be a belief, value, or principle that the audience grants.

9. The Power of Audience-based reasons
Audience-based reason and writer-based reason should match
A WRITER-BASED STATEMENT: You should become a vegetarian because doing so will help reduce the needless suffering of animals
UNDERLYING ASSUMPTION: It is wrong to cause the suffering of animals
To address the meat-eaters, we should also consider some AUDIENCE-BASED REASONS by adding more enthymemes:
You should become a vegetarian because doing so may help you lower your cholesterol (HEALTH VALUES)
You should become a vegetarian because doing so will significantly lower your carbon footpring (ENVIRONMENTAL VALUES)
i.e. In order to persuade the audience, we need to consider the underlying assumptions

10. Class Discussion-4 / Identifying Underlying Assumptions and Choosing Audience-Based Reasons (p.13)
Part 1. Identify the unstated assumption that the audience must supply in order to make the following enthymemes persuasive.
Example
Enthymeme: Rabbits make good pets because they are gentle.
Underlying assumption: Gentle animals make good pets.
1. We shouldn’t elect Joe as committee chair because he is too bossy.
2. Airport screeners should use racial profiling because doing so will increase the odds of stopping terrorists.
3. Racial profiling should not be used by airport screeners because it violates a person’s civil rights.
4. We should strengthen the Endangered Species Act because doing so will preserve genetic diversity on the planet.
5. The Endangered Species Act is too stringent because it severely damages the economy.

11. Part 2: Decide which of the two reasons would be more persuasive to the specified audience. How might the reason not chosen be effective for a different kind of audience?
1. Audience: people who advocate a pass/fail grading system on the grounds that the present grading system is too competitive
a. We should keep the present grading system because it prepares people for the dog- eat-dog pressures of the business world.
b. We should keep the present grading system because it tells students that certain standards of excellence must be met if individuals are to reach their full potential.
2. Audience: environmentalists
a. We should support fracking for natural gas because doing so will help reduce our dependence on foreign sources of oil.
b. We should support fracking for natural gas because doing so will provide a greener “bridge fuel” that will give us time to develop better renewable technologies.

12. The Toulmin System
There are terms aside from the claim and reason in the Toulmin System
Warrant: the value, belief, or principle that the audience has to hold if the soundness of the argument is to be guaranteed or warranted

13. Grounds: supporting evidence that causes an audiene to accept your reason (facts, statistics, examples, etc)

14. Backing: the argument that supports the warrant (especially if the audience will question or doubt the warrant)

15. Conditions of Rebuttals: writers’ awareness of the arguments from the skeptics

16. Qualifier: not proving the claim with strong words; instead using hedges such as likely, probably…
E.g.
Except for limited cases of scientific research, dolphins and orcas should not be held in captivity,
We should consider raising the minimum wage because doing so may be one possible way to reduce poverty
Just keep in mind:
No argument is 100 percent conclusive.

17. Class Discussion-5 / Developing Enthymemes with the Toulmin Schema Working individually or in small groups, imagine that you have to write arguments developing the five enthymemes listed in the For Class Discussion exercise on pages 13–14.  Use the Toulmin schema to help you determine what you need to consider when developing each enthymeme. We suggest that you try a four-box diagram structure as a way of visualizing the schema. We have applied the Toulmin schema to the first enthymeme: “We shouldn’t elect Joe as committee chair because he is too bossy.”