argument-evaluation

# Argument Evaluation

An argument is a set of statements in which some (the premises) are offered as reasons for believing another (the conclusion). Critical thinkers evaluate arguments by reconstructing them, testing their logical form, checking the truth of the premises, and engaging with the strongest version of the opposing case. This skill provides a systematic procedure for doing all four.

**Agent affinity:** paul (overall framing, elements of reasoning), elder (structural reconstruction)

**Concept IDs:** crit-argument-structure, crit-deductive-reasoning, crit-inductive-reasoning, crit-charitable-interpretation

## The Evaluation Toolbox at a Glance

| # | Operation | Purpose | Key signal |
|---|---|---|---|
| 1 | Premise extraction | Pull claims that support the conclusion | "Because," "since," "given that" |
| 2 | Conclusion extraction | Identify what is being argued for | "Therefore," "so," "thus," "hence" |
| 3 | Argument mapping | Show dependency structure | Some premises support sub-conclusions |
| 4 | Reconstruction | Restate in standard form | Numbered premises, explicit conclusion |
| 5 | Validity check | Does conclusion follow if premises are true? | Counterexample to form |
| 6 | Soundness check | Are the premises actually true? | Independent fact check |
| 7 | Strength check | For inductive arguments, how probable is the conclusion? | Sample quality, base rates |
| 8 | Steel-manning | Reconstruct the strongest version | Add missing support the author could have given |
| 9 | Hidden premise detection | Find the unstated assumption | The argument leaks if the premise is removed |
| 10 | Scope check | Does the conclusion overreach the evidence? | "All" from "some," universal from single case |

## Operation 1 — Premise Extraction

**Pattern:** Isolate statements the author offers as reasons. These are the building blocks of the argument.

**Indicator words:** "because," "since," "given that," "in light of," "as shown by," "for the reason that."

**Worked example.** *"Because the economy is slowing and interest rates are still high, a recession is likely within six months."*

Premises:
- P1: The economy is slowing.
- P2: Interest rates are still high.

Notice that indicator words are cues, not guarantees. Some premises appear without indicators; some indicator words are used rhetorically without introducing real premises.

## Operation 2 — Conclusion Extraction

**Pattern:** Identify the statement the premises are meant to support.

**Indicator words:** "therefore," "thus," "so," "hence," "it follows that," "we can conclude," "which shows."

**Worked example (continued).** The conclusion of the example above is:
- C: A recession is likely within six months.

**Common mistake.** Treating a rhetorical question as a conclusion. "Why should we trust them?" is not a conclusion; it is a question that implies one.

## Operation 3 — Argument Mapping

**Pattern:** Show which premises support which conclusions, including intermediate sub-conclusions.

**Worked example.** *"Social media harms adolescent mental health because it promotes comparison with curated images. Therefore, schools should restrict phone use during the day."*

```
P1: Social media promotes comparison with curated images.
                |
                v
SC1: Social media harms adolescent mental health.  (sub-conclusion)
                |
                v
C:  Schools should restrict phone use during the day.
```

The map reveals that the argument has two logical steps, only one of which was explicitly signaled. Mapping often exposes gaps.

## Operation 4 — Reconstruction in Standard Form

**Pattern:** Restate the argument as numbered premises followed by a single conclusion.

**Worked example.** *"You shouldn't drink the water here. The EPA says it has lead contamination."*

Standard form:
```
P1. The EPA says this water has lead contamination.
P2. [Hidden] Water with lead contamination is unsafe to drink.
P3. [Hidden] You should not drink unsafe water.
C.  You should not drink the water here.
```

Reconstruction often surfaces hidden premises. An argument is not a shapeless cloud of sentences — it is a chain, and every link needs to be visible before you can test it.

## Operation 5 — Validity Check

**Pattern:** Ask whether, if the premises were all true, the conclusion would have to be true.

**Logical basis:** Validity is a property of the argument's form, not of its content. An argument can be valid with false premises, and invalid with true premises.

**Worked example (valid).**
```
P1. All ravens are birds.
P2. All birds have feathers.
C.  All ravens have feathers.
```
This is valid because the form (All A are B; All B are C; therefore All A are C) guarantees the conclusion whenever the premises are true.

**Worked example (invalid).**
```
P1. All ravens are birds.
P2. Some birds are flightless.
C.  Some ravens are flightless.
```
The premises are both true, but the conclusion does not follow. There is no logical guarantee connecting the particular birds that are flightless to ravens specifically.

**The counterexample test.** To show an argument form is invalid, produce an instance with the same form where the premises are true and the conclusion is false.

## Operation 6 — Soundness Check

**Pattern:** An argument is sound if and only if it is valid and all premises are actually true.

Validity is a relationship among statements. Soundness is validity plus real-world accuracy. A valid argument with a false premise proves nothing about the world.

**Worked example.**
```
P1. All mammals lay eggs.          [FALSE]
P2. Whales are mammals.            [TRUE]
C.  Whales lay eggs.               [Valid form, unsound argument]
```
The form is valid. The first premise is false. The conclusion is false. Soundness failed at P1.

**Discipline.** When evaluating a valid argument, interrogate each premise independently. Which evidence supports it? Which evidence could refute it? What would change your mind about t