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Structure and Analysis, Part 1

As we saw in Module One, when we think of the word “argument,” we typically think of disagreement on an issue. Many of us would probably imagine two individuals getting into a heated debate, or even a

yelling match, and call this an “argument.”

However, in logic, we typically use the word

‘argument’ to refer to a series of statements in which one or more propositions are being used to support another proposition. The supporting statements, or reasons, are called premises. The main point, or the proposition these premises are supporting, is called the conclusion. Each of the

propositions is a complete statement that may be true or false.

Example #1

P1: The world appears flat.

P2: All things that appear flat are in fact flat.

C: Therefore, the world is in fact flat.

In the argument above, both premise P1 and P2 are supporting the conclusion that the world is in fact flat. However, the propositions in P1 and P2 are subject to evidence to determine whether they are true

or false. In this case, although premise P1 is arguably true based on the appearance of the world to the human eye, we know from scientific evidence that the earth, which appears flat in casual observation, is

in fact spherical. So the premise P2 is false based on empirical evidence that proves that not all things appearing flat are in fact flat. We will cover evaluating arguments in the next module.

Example #2

Sentences can include many propositions. For example, consider the following sentence about a potential job candidate:

Chuck is experienced, but unfriendly and lazy.

This single statement actually contains three propositions about Chuck, each of which can be judged

either true or false. They are:

P1: Chuck is experienced.

P2: Chuck is unfriendly.

P3: Chuck is lazy.

However, this sentence, standing alone, does not comprise a complete argument, because the sentence does not relate these propositions to a conclusion about Chuck. A completed argument might be:

P2: Chuck is unfriendly.

P3: Chuck is lazy.

C: Therefore, Chuck would not be the best candidate for the job.

This argument uses the propositions as premises in order to support a conclusion: namely, that Chuck would not be the ideal candidate for the position.

Arguments come in different types, two of which we will study at length in this course.

Deductive arguments are arguments in which the premises are linked and, when taken together, the conclusion of

the argument would necessarily follow from the premises (assuming they are true). The argument above about the world being flat is a deductive argument: Assuming the premises are true, if we took them

together, the conclusion would necessarily follow.

In inductive arguments, we are given pieces of evidence that provide support for the conclusion, but they may not necessarily prove that the conclusion will follow. The argument above about the job candidate Chuck is one example of an inductive argument: It provides statements that are unrelated to one another, but taken as a whole (and despite the positive factor of his experience) provide support for the conclusion that he should not be hired. As opposed to a deductive argument, the premises of an inductive argument do not need to be linked to one another. Both inductive and deductive arguments

will be studied at length in Modules Five and Six.

What Kinds of Premises Exist, and What Makes a Premise a Good One?

Premises, as we have covered, are propositions that provide support for a conclusion. Different kinds of

premises include:

• Descriptive premises, which are based on empirical or scientific facts. (E.g., the earth is spherical in shape.)

• Prescriptive premises, which are value statements of what we should do.

(E.g., we should strive for gender equality in employment practices.)

• Analogical premises, which are based on comparisons of similar things. (E.g., a jaguar runs quickly. A cheetah has a similar body structure to the jaguar, so it must al

so run quickly.)

• Definitional premises, which contain the definition of a key term. (E.g., “Affirmative action is a policy to increase opportunities for women and minorities in college admissions and employment” [Boss, 2012, p. 172].)

In an argument, the conclusion (or main point of the argument) is the component that is supported by one or several premises. The premise is a proposition that provides support or evidence for why we