Week 1 · Chapter

Chapter 1 — What Critical Thinking Is: Claims, Arguments & Explanations

Critical Thinking Free sample edition

The module's primary reading · ~35–45 minutes · Objective 1 (identify claims and arguments in everyday and academic passages, distinguishing arguments from explanations, reports, and unsupported assertions, and locate premises and conclusions with and without indicator words) · Read it first this week; the lecture, the slides, the tutorial, the quiz, and the Argument Workshop all build on it.

In plain language

This week is about noticing exactly what people ask you to believe and why. Critical thinking (the habit of checking a claim and its support before you accept it) is a set of moves you can learn, not a talent you either have or lack. You will learn to spot a claim (a sentence that is either true or false) and an argument (reasons offered to get you to accept a claim). You will also learn to tell an argument from an explanation (reasons why something everyone already accepts is so). By the end of the week you will find the reasons and the main claim in a short campus proposal, which is the first step before anyone can judge whether the reasons are any good.

Why you already care about this

It is 11 p.m., and a group chat of 6 friends lights up. One friend writes that the new campus coffee cart "is a rip-off" because a latte costs 2 dollars more than at the cafe across the street. A second friend posts 3 laughing emojis. A third writes, "So we should all boycott it." In under a minute, the chat has a claim, a reason, a joke, and a proposal for action.

You sort messages like these all day without naming what you are doing. Some messages report facts. Some vent a feeling. Some ask you to do something, and a few actually give you reasons. The trouble is that reasons and non-reasons look alike on a phone screen, and the loudest message is not always the best supported.

This chapter gives you names and tests for those moves. They are the first tools in a course that will hand you one new test a week, and every later test starts from the skill you build here: finding what is being claimed and what is offered in support.

By the end of this chapter you will be able to:

say what critical thinking is in one sentence, as three questions you can ask;
sort sentences into claims, questions, commands, and reports of a feeling;
explain why calling something "an opinion" does not end the conversation about it;
pick out the premises and the conclusion of an argument;
tell an argument from an explanation, a report, and an unsupported assertion;
use indicator words as clues and find a conclusion when no indicator appears;
find the conclusion and the three stated reasons in the running question's passage.

Carry this line with you: find the argument first; judge it later — not the reverse.

Where we are

This week: what critical thinking is, what a claim is, what an argument is, how arguments differ from explanations, reports, and unsupported assertions, how indicator words help, and the first look at the course's running question.
How they connect: this chapter is the foundation, so there is no earlier week to lean on; every later week starts by finding the argument you learn to find here.
Where we're going next: Week 2, Analyzing Arguments, takes the premises and conclusion you find this week and writes them out in a fixed layout so each step can be checked.

This is the first week of the course, so nothing earlier is assumed. You need no background in logic or philosophy, and the only math is multiplying and adding small whole numbers. What you do need is a willingness to slow down for a few seconds before you agree or disagree with something. That pause is where every test in this course lives.

1. Ask three questions: what critical thinking is

Picture a roommate who comes home and announces, "The landlord is raising the rent next month, so we need to find a third roommate." Before you start texting friends, three questions are worth asking. What exactly is being claimed? What reasons are offered for it? And how good are those reasons?

Those three questions are the whole course in miniature.

Critical thinking is the habit of asking what a claim says, what supports it, and how good that support is before you accept it. It is a set of tests you can run, not a personality trait.

That last sentence matters. Critical thinking is not being negative, and it is not winning arguments. A critical thinker can end up agreeing with the roommate. The difference is that the agreement comes after the three questions, not instead of them.

Worked example — the three questions on the roommate's announcement. Run the three questions on the roommate's sentence.

What is claimed? Two things: that the rent is going up next month, and that the two of you need to find a third roommate. The second is the main claim, the one the roommate wants you to act on.
What supports it? One reason is stated: the rent increase.
How good is that support? You cannot judge that yet without more facts. How big is the increase? Could you cover it another way? Is the increase confirmed in writing?

In words: the roommate gave one reason for one main claim, and the third question shows what you would need to know before agreeing.

This week you practise the first two questions. The third, judging how good the support is, starts in Week 3 and runs to the end of the course.

Misconception check. Students often think critical thinking means criticizing, so a "critical" reader is one who rejects things. That is tempting, because "critical" sounds like "critic." But the course uses the word in its older sense of careful judgment. A careful reader can accept a well-supported claim and reject a poorly supported one, and both are critical thinking.

Memory hook: what is claimed, what supports it, how good is the support.

2. Sort sentences: claims, opinions, and non-claims

Look at four sentences someone might say at a gym's front desk:

"The pool closes at 9 p.m."
"Is the pool open on holidays?"
"Sign this waiver before you swim."
"I'm so tired of this place."

Only the first one can be true or false as it stands. You could check the posted hours and find out. The second asks, the third orders, and the fourth reports how the speaker feels.

A claim is a sentence that is either true or false. Questions, commands, and reports of a feeling taken as a feeling are not claims, though a question or a command can carry an implied claim.

That last part needs an example. "Why do you always leave the lights on?" is a question, but it carries an implied claim: that you always leave the lights on. A careful reader notices the implied claim and asks whether it is true.

Now the tricky word. People often say "that's only your opinion" to end a disagreement. In this course, an opinion is a claim someone holds. Calling a claim an opinion does not take it out of evaluation: the reasons offered for an opinion can be strong or weak, and the course grades the reasons, not whether you share the opinion.

Worked example — sort the product review (illustrative). An online review of a pair of running shoes reads: "These shoes are the best I've ever owned. Did the company forget to include insoles? Buy them anyway. I love the color."

"These shoes are the best I've ever owned" is a claim. It is the reviewer's opinion, but it is still true or false about the reviewer's shoes, and you can ask what supports it.
"Did the company forget to include insoles?" is a question. It carries an implied claim worth checking: the box came without insoles.
"Buy them anyway" is a command. It carries an implied claim: the shoes are worth buying.
"I love the color" reports a feeling. Taken as a report of a feeling, it is not a claim you could argue about.

In words: the review holds 1 stated claim, 1 question, 1 command, and 1 report of a feeling, and two of the non-claims carry implied claims you could check.

Misconception check. Students often think an opinion is a claim that cannot be evaluated, so "it's my opinion" ends the discussion. That is tempting, because people do differ on matters of taste. But an opinion is a claim someone holds, and the reasons behind it can still be strong or weak. "The shoes are the best I've owned, because they lasted 3 years of daily runs" has better support than "the shoes are the best, because the box was pretty."

Memory hook: an opinion is still a claim, and claims have reasons.

3. Spot an argument: premises and a conclusion

Suppose a city council member (an illustrative scenario) says: "We should add a crosswalk at the corner of the park. Kids cross there every afternoon, and drivers speed through that stretch." That is more than a claim. It is a claim with reasons attached, offered to get the council to agree.

An argument is a set of claims in which one or more (the premises) are offered as reasons to accept another (the conclusion).

Two terms come out of that definition. A premise is a claim offered as a reason to accept another claim. The conclusion is the claim the premises are offered to support, the one the arguer wants the audience to accept.

An argument is not a fight. It is a structure: reasons pointing at a conclusion. Two people can calmly exchange arguments, and one angry person can shout for an hour without making a single argument.

Two neighbors often get mistaken for arguments. A report tells what happened or what is the case without offering any claim as a reason to accept another. An unsupported assertion is a claim stated with no reason offered for accepting it; it may be true or false, but it is not an argument.

Worked example — sort the three workplace messages (illustrative). A team at a print shop gets three messages in one morning.

"The large printer jammed twice yesterday, and the technician replaced a roller." This tells what happened. No claim is offered as a reason for another, so it is a report.
"This new scheduling app is a disaster." One claim, no reason. It is an unsupported assertion. It might be true, but nothing is offered to show it.
"We should move the weekly meeting to the morning, since three of the five staff members leave by noon." The conclusion is "we should move the weekly meeting to the morning". The premise is that three of the five staff members leave by noon. This is an argument.

In words: only the third message offers a reason for accepting a claim, so only the third is an argument.

Misconception check. Students often think a long passage is one argument. That is tempting, because a paragraph looks like a single unit. But a passage can hold two arguments with two conclusions. A gym flyer (illustrative) might argue "the morning class is less crowded, so it is the better class for beginners" and then, in a separate sentence, "our new rowing machines are quieter, so you should try them." Count the conclusions before you assume there is only one.

Memory hook: no reason offered, no argument.

4. Tell an argument from an explanation: is it in doubt?

Here is a pair of sentences about a soccer game. Read them slowly:

"The game was canceled because the field flooded."
"The game will be canceled, because the field is flooding."

Both use the word "because." Both mention a field and a canceled game. Yet they do different jobs.

In the first sentence, everyone already knows the game was canceled. The sentence tells you why it happened. In the second, the cancellation has not been announced, and the speaker is giving you a reason to expect it. One sentence explains; the other argues.

An explanation is a set of claims that gives reasons why something already accepted is so, rather than reasons to believe something still in question.

The test is a single question: is the claim being supported in doubt for the audience? If the audience already accepts it, the reasons explain. If the audience still needs convincing, the reasons argue. The same "because" sentence can be either, depending on whether the thing it supports is in doubt for the people hearing it.

Worked example — run the doubt test on three sentences. Ask of each one whether the supported claim is already accepted.

A weather report says: "Flights were delayed this morning because fog covered the airport." The delays already happened and nobody disputes them. The sentence explains.
A coach says to the team: "We'll lose the next match unless we fix our passing, because the other team presses hard." The loss has not happened and is in question. The sentence argues.
A trainer tells a client: "Your legs are sore because yesterday's workout was your first in a month." The soreness is already accepted; the client feels it. The sentence explains.

In words: when the supported claim is already accepted, you have an explanation; when it is still in doubt for the audience, you have an argument.

An honesty note: some sentences sit on the line. "The store closed because the rent went up" explains to a reader who knows the store closed, but argues to a reader who thinks the owner retired by choice. The audience matters, so when a case is borderline, say which audience you have in mind and give your reason.

Misconception check. Students often read every explanation as an argument, and so they try to "disagree" with a sentence like "the game was canceled because the field flooded." That is tempting, because explanations and arguments both use "because" and both give reasons. The cure is the doubt test. If nobody doubts that the game was canceled, the sentence is not trying to convince anyone of it; it is telling you why.

Memory hook: explanations answer "why is it so?"; arguments answer "why believe it?"

5. Read indicator words: clues, not proof

Writers often leave signposts. In "the shelter is full, so we should open the overflow room," the word "so" tells you a conclusion is coming. In "we should open the overflow room, since the shelter is full," the word "since" tells you a premise is coming.

Words that often signal a premise are premise indicators. The common ones are because, since, given that, and for.

Words that often signal a conclusion are conclusion indicators. The common ones are so, therefore, thus, hence, and which shows that.

Indicators help, but they do not decide. Two cautions keep them in their place. First, "because" also introduces explanations, as Section 4 showed. Second, many arguments carry no indicator at all. When that happens, ask: what is the writer trying to get me to accept, and what is offered as the reason? Whatever fills the first half is the conclusion, wherever it sits in the passage.

Worked example — a recipe blog with no indicators (illustrative). A recipe blog says: "Use cold butter in this pie crust. Warm butter melts into the flour. Cold butter leaves small pieces that turn to steam in the oven and make the crust flaky."

Look for indicators. There is no "so," no "because," and no "therefore."
Ask what the writer wants you to accept. That you should use cold butter. That is the conclusion, and it comes first.
Ask what is offered as the reason. Warm butter melts into the flour, and cold butter leaves small pieces that make the crust flaky. Those are the premises.

In words: the passage is an argument with its conclusion in the first sentence and two premises after it, and not one indicator word appears.

Worked example — a "since" that is not a premise. "Since the new bridge opened, traffic downtown has been lighter." Here "since" means "from the time when," not "because." Nothing is offered as a reason, so it is a report about traffic, not an argument.

Misconception check. Students often think "because" always marks a premise. That is tempting, because "because" is the most common premise indicator. But "because" also introduces explanations ("the game was canceled because the field flooded"), and "since" can be a time word. An indicator is a clue to check, not a verdict to trust.

A limitation worth saying out loud: the indicator lists are a classroom tool, not a complete dictionary. Writers use dozens of other signals ("it follows that," "as shown by," "the upshot is"), and the doubt test and the "what am I meant to accept?" question work on all of them.

Memory hook: indicators are clues, not proof.

6. Find the running question's conclusion and reasons

Every week this term, you will run that week's test on one shared argument, called the running question: should the campus library stay open around the clock during finals week? It is an illustrative question; the newsletter below has no real author, and the course takes no side on the answer.

Here is the passage as it appears in an imagined campus newsletter (illustrative):

The campus library should stay open around the clock during finals week. During finals week many students need a quiet, safe place to study late at night. The library is the only quiet, safe, well-lit study space on campus large enough to meet that need. Keeping the library open overnight for the five nights of finals week costs about 1,600 dollars in staff wages.

Your job this week is not to agree or disagree. It is to find the parts.

A stated reason is a premise that a passage says out loud, as opposed to one the reader has to supply.

Worked example — the running question's newsletter passage. Work through the passage one sentence at a time.

Find the conclusion. Ask what the writer wants you to accept. The first sentence does that job: "the campus library should stay open around the clock during finals week." It comes first and carries no conclusion indicator.
Stated reason 1. During finals week many students need a quiet, safe place to study late at night.
Stated reason 2. The library is the only quiet, safe, well-lit study space on campus large enough to meet that need.
Stated reason 3. Keeping the library open overnight for the five nights of finals week costs about 1,600 dollars in staff wages.
Tally. 1 conclusion and 3 stated reasons, so the passage holds 1 + 3 = 4 claims.
Check the one figure. The 1,600 dollars comes from 2 staff working 8 hours a night for 5 nights at 20 dollars an hour. Step by step: 2 staff × 8 hours a night = 16 staff hours a night; 16 × 5 nights = 80 staff hours; 80 × 20 dollars an hour = 1,600 dollars. The figure checks out.
Argument or explanation? The overnight hours are a proposal, still in question for the newsletter's readers. So the passage argues; it is not explaining something everyone already accepts.

In words: the passage is an argument with one conclusion and three stated reasons; whether those reasons are good enough is a question for later weeks.

Notice what you did not do. You did not decide whether 1,600 dollars is a lot or a little. You did not decide whether students should study all night. Finding an argument is not judging it, and it is certainly not agreeing with it. A student who opposes overnight hours should find exactly the same conclusion and the same three reasons as a student who supports them. The same goes for the coffee-cart chat from the start of this chapter. The friends who want a boycott and the friends who like the lattes should first agree on what the argument says. Only then can they usefully argue about whether it is right.

Misconception check. Students often think that finding an argument's parts means taking its side, so a student who disagrees with the conclusion "finds" fewer reasons. That is tempting, because it is hard to state a view you reject. But the parts of an argument are on the page for everyone. The course grades how accurately you find them, never which side you are on.

Memory hook: find the argument first; judge it later.

Key terms

critical thinking — The habit of asking what a claim says, what reasons support it, and how good those reasons are before accepting it; it is a set of tests a person can run, not a personality trait. (first used: 1. Ask three questions: what critical thinking is)
claim — A sentence that is either true or false; questions, commands, and reports of a feeling taken as a feeling are not claims, though a question or a command can carry an implied claim. (first used: 2. Sort sentences: claims, opinions, and non-claims)
opinion — A claim someone holds; calling a claim an opinion does not take it out of evaluation, because the reasons offered for it can still be strong or weak. (first used: 2. Sort sentences: claims, opinions, and non-claims)
argument — A set of claims in which one or more, the premises, are offered as reasons to accept another, the conclusion. (first used: 3. Spot an argument: premises and a conclusion)
premise — A claim offered as a reason to accept another claim in an argument. (first used: 3. Spot an argument: premises and a conclusion)
conclusion — The claim in an argument that the premises are offered to support, the one the arguer wants the audience to accept. (first used: 3. Spot an argument: premises and a conclusion)
report — A passage that tells what happened or what is the case without offering any claim as a reason to accept another. (first used: 3. Spot an argument: premises and a conclusion)
unsupported assertion — A claim stated with no reason offered for accepting it; it may be true or false, but it is not an argument. (first used: 3. Spot an argument: premises and a conclusion)
explanation — A set of claims that gives reasons why something already accepted is so, rather than reasons to believe something still in question. (first used: 4. Tell an argument from an explanation: is it in doubt?)
premise indicator — A word or phrase such as because, since, given that, or for that often signals that a premise follows; it is a clue, not proof, since because also introduces explanations. (first used: 5. Read indicator words: clues, not proof)
conclusion indicator — A word or phrase such as so, therefore, thus, hence, or which shows that, which often signals that a conclusion follows. (first used: 5. Read indicator words: clues, not proof)
running question — The illustrative question this course argues all term, whether the campus library should stay open around the clock during finals week, so that each week's test is run on the same argument. (first used: 6. Find the running question's conclusion and reasons)
stated reason — A premise that a passage says out loud, as opposed to one the reader has to supply. (first used: 6. Find the running question's conclusion and reasons)

Summary

Critical thinking asks three questions: what is claimed, what supports it, and how good the support is.
A claim is true or false; questions, commands, and reports of a feeling are not claims.
An opinion is a claim someone holds, and its reasons can still be judged.
An argument offers premises as reasons for a conclusion.
A report tells what happened; an unsupported assertion gives no reason.
An explanation says why an accepted fact is so; an argument says why to believe something in doubt.
Indicator words are clues, not proof; "because" also introduces explanations.
When no indicator appears, ask what the writer wants you to accept.
The running question's passage has one conclusion and three stated reasons.

Check your understanding

Work these before looking at the answers — they are ungraded, and the answers (with reasoning) are at the bottom of the page.

A sign at a bike shop (illustrative) reads: "Helmets are 20 percent off this week. Have you checked your helmet's strap lately? Ask us for a free fitting. Old helmets lose their padding over time." Sort each sentence as a claim, a question, or a command, and name any implied claim.
A text from a cousin (illustrative) says: "The bakery on Elm Street closed because the owner moved to another state." Is this an argument or an explanation? Say what you would need to know about the audience to be sure.
A neighborhood newsletter (illustrative) says: "The community pool should open an hour earlier. Early-shift workers have no time to swim after work, and the morning lifeguard is already on site by 6 a.m." Find the conclusion and the premises. Does it use any indicator words?
A community garden plans to buy 4 rain barrels at 35 dollars each and 3 bags of soil at 12 dollars each. A member argues: "The supplies cost under 200 dollars, so the club can afford them from its 250-dollar fund." Check the cost claim with the arithmetic shown, then name the conclusion.

Answers (worked reasoning — read after attempting)

"Helmets are 20 percent off this week" is a claim; you could check the price tags. "Have you checked your helmet's strap lately?" is a question; it carries an implied claim that straps are worth checking. "Ask us for a free fitting" is a command; it carries an implied claim that fittings are free. "Old helmets lose their padding over time" is a claim. So the sign holds 2 stated claims, 1 question, and 1 command.
For most audiences it is an explanation: the bakery's closing is already known, and the text says why it happened. It would be an argument only if the cousin were trying to convince someone who doubted the bakery had closed. The doubt test decides it: is "the bakery closed" in doubt for the person reading?
The conclusion is "the community pool should open an hour earlier." The premises are that early-shift workers have no time to swim after work and that the morning lifeguard is already on site by 6 a.m. There are no indicator words. You find the conclusion by asking what the writer wants you to accept.
Rain barrels: 4 × 35 = 140 dollars. Soil: 3 × 12 = 36 dollars. Total: 140 + 36 = 176 dollars, which is under 200, so the cost claim checks out. The conclusion is "the club can afford them from its 250-dollar fund"; the premise is that the supplies cost under 200 dollars. Checking the arithmetic tells you the premise is true. Whether the club should spend the money is a different question.

Next up in this module: the lecture, the slide deck, the Readings & Resources page, the lecture tutorial, and the practice set. Next week the parts you found go into standard form, the method of writing each premise on its own numbered line above the conclusion.

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