1.2 Structure and Types of Arguments

Argument Structure

Arguments are the building blocks of logical reasoning. Every argument has the same basic job: one or more statements (called premises) are offered as reasons to accept another statement (the conclusion). What makes arguments interesting in formal logic is that they come in different structural patterns, and recognizing those patterns is the first step toward evaluating whether an argument actually works.

Components of an Argument

Premises are statements offered as evidence or reasons to support a conclusion. They can be explicitly stated or sometimes left implied. Most arguments have more than one premise.

The conclusion is the main claim the argument is trying to establish. The premises point toward it. While conclusions often appear at the end of an argument, they can show up first, with the supporting reasons following after. Don't assume position in a sentence tells you what's a premise and what's a conclusion.

Types of Argument Structures

Simple arguments have a single premise (or a small, tightly connected set) leading to a single conclusion. They're straightforward to identify:

Complex arguments involve multiple premises and may contain sub-arguments or intermediate conclusions that feed into the main conclusion. Analyzing these requires you to trace which statements support which. Consider this example:

Here, "Socrates is mortal" is an intermediate conclusion (supported by the first two premises) that combines with "Socrates is wise" to reach the final conclusion.

Argument Types

Convergent Arguments

In a convergent argument, each premise independently supports the conclusion. Think of multiple pillars holding up a roof: if you remove one pillar, the others still provide support. The premises don't depend on each other.

Either premise on its own gives you a reason to accept the conclusion. Removing one doesn't destroy the other's support.

Linked Arguments

In a linked argument, the premises work together and depend on each other. Remove any one premise and the support for the conclusion collapses. The premises are like links in a chain: each one is necessary.

Neither premise supports the conclusion by itself. "All mammals are warm-blooded" alone tells you nothing about whales, and "Whales are mammals" alone tells you nothing about being warm-blooded. You need both premises working together.

Serial Arguments

A serial argument forms a chain: the conclusion of one sub-argument becomes a premise in the next. Each link in the chain must hold for the final conclusion to follow.

Notice how "Socrates is mortal" is first a conclusion (from the first two premises), then becomes a premise that combines with "Socrates is wise" to reach the final conclusion.

Argument Indicators

Identifying Arguments through Indicator Words

Indicator words are words or phrases that signal the role a statement plays in an argument. They're your best shortcut for quickly mapping out an argument's structure.

• Premise indicators introduce premises: because, since, given that, as, for, assuming that
• Conclusion indicators introduce conclusions: therefore, thus, hence, so, consequently, as a result, it follows that

Here's an example with both types at work:

"Because" flags the premise (he stayed up all night). "Therefore" flags the conclusion (he'll struggle to focus).

When Indicator Words Are Absent

Not all arguments use indicator words. Some passages state premises and conclusions without any explicit signals. In those cases, you need to ask yourself: Which statement is being supported, and which statements are doing the supporting? The logical relationships between the statements matter more than any single word. Practice identifying arguments both with and without indicators, since exam questions will test both.