Unit 12: Deductive and Non-Deductive Arguments

Unit 12 classifies arguments according to "semantic" types: "deductive" and "non-deductive." These terms refer to the manner in which conclusions are derived from the premises that support them.  In a deductive argument the premises literally guarantee the exact wording of the conclusion(s).  In a non-deductive argument, the premises make the conclusion(s) only likely or probable., not guaranteed.

The strongest argument is a deductive argument since there is no alternative to the conclusion that is generated by the premises that lead to it.  Non-deductive arguments can be very convincing as well, but there is always a percentage of a chance that the conclusion will not hold true, or that there may be other alternatives.  Here are some examples:

A Deductive Argument:

1) If it rains today, we will leave tomorrow.
2) It is raining today.
3) We will leave tomorrow.

Note that, given premises #1 and #2, there is no other alternative for the conclusion #3.

A Non-Deductive Argument

1) English 1301 is a difficult course.
2) I am taking 18 hours this semester.
3) I work forty hours a week.
4) I should drop English 1301.

Note that while the premises make the conclusion likely or probable, nevertheless, the conclusion is one of only a number of possible conclusions (examples: "I need to quit work to devote more time to English 1301," "I need to drop another course so that I can concentrate on English 1301," etc.)

Instructional Materials
I have provided an outline of argument, "Argument - Basic Definitions," to supplement the discussion in your textbook.  For those interested in a more extensive analysis, see my essay and exercises included in "Notes on Argument."

Readings in The Longman Writer
Read "Part 3: Argument and Persuasion" pages 461 - 552.

Assignment
Read "Argument in 'The Declaration of Independence.'"  Note the two different types of arguments represented in the four arguments of the document.

What You Will Submit
Nothing.

Due Dates for Submission
Not applicable.

Student Learning Outcomes
The following Student Learning Outcomes are addressed in this exercise:

1. Students will identify the purpose of writing while considering an appropriate tone, language and audience

.