Lecture: What Critical Thinking Is: Claims, Arguments & Explanations
Lecture script · about 15–20 minutes spoken · Week 1
Opening
Think about the last time someone asked you to believe something or do something. Maybe a friend in a group chat said the new coffee cart is a rip-off and everyone should boycott it. Maybe a manager sent a memo about a schedule change. Maybe a headline told you a food is good for your heart. Every one of those moments asks something of you.
Whether you're a nursing student weighing a health headline, a business major reading a manager's memo, or a voter reading a city proposal, the first step is always the same. You find exactly what is being claimed, and you find what reasons are offered for it. That sounds small. It turns out to be most of the work.
This is the first week of the course, so we start at the foundation. In this lecture I'll tell you what critical thinking is, show you how to spot a claim, and show you what turns a few claims into an argument. Then we'll separate arguments from explanations, look at the little signal words writers use, and meet the argument we'll carry through the whole course. Next, in Week 2, we'll take the arguments you learn to find here and lay them out so each step can be checked.
1. What critical thinking is
Picture your roommate walking in and announcing, "The landlord is raising the rent next month, so we need a third roommate." Before you start texting friends, three questions are worth a few seconds. What exactly is being claimed? What reasons are offered? 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.
I want to stress that last part. Critical thinking is closer to checking your mirrors before you change lanes than to perfect pitch. Nobody is born doing it. You learn the moves and practise them until they become a habit.
Let's run the three questions on the roommate. What's claimed? Two things: the rent is going up, and you need a third roommate. The second is the main claim, the one you're being asked to act on. What supports it? One reason: the rent increase. How good is that support? You can't tell yet. You'd want to know how big the increase is, whether you could cover it another way, and whether it's confirmed in writing.
Notice that none of this is negative. You might end up agreeing with your roommate. The difference is that the agreement comes after the three questions, not instead of them. A careful reader accepts well-supported claims and rejects poorly supported ones, and both of those are critical thinking.
In this course you'll practise the first two questions this week. The third, judging how good the support is, starts in Week 3 and runs to the end of the course.
Pause and try this. A classmate says, "Critical thinking means finding what's wrong with everything." What's the problem with that description?
Hold the three questions in mind before you decide.
Here's the answer. It mistakes criticizing for careful judgment, because a critical thinker can accept a claim once the three questions show its support is good.
So keep the three questions close: what is claimed, what supports it, and how good is that support.
2. Claims, opinions, and non-claims
Let's start with the smallest piece. Imagine four things 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." And, "I'm so tired of this place."
Only the first one can be true or false as it stands. You could walk over to the posted hours and check. The second asks something. The third tells you to do something. The fourth tells you how the speaker feels.
That gives us our first term. 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 is sneaky, so here's an example. "Why do you always leave the lights on?" is a question. But tucked inside it is a claim: that you always leave the lights on. A careful listener notices the hidden claim and asks whether it's true.
Now, the tricky word. You've probably heard someone end a disagreement with "well, that's only your opinion." 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.
Here's a way to feel the difference. Two people say a pair of running shoes is the best they've ever owned. One says so because the shoes survived years of daily runs. The other says so because the box was pretty. Same opinion. Very different support. Saying "it's my opinion" never makes that difference go away.
Pause and try this. A running-shoe review says, "Did the company forget to include insoles?" Is that a claim? And is there a claim hiding inside it?
Think about what the question takes for granted.
Here's the answer. It's a question, not a claim, but it carries an implied claim worth checking: that the box came without insoles.
An opinion is still a claim, and claims have reasons.
3. What makes an argument
A single claim is a brick. An argument is what you get when some bricks are stacked to hold another one up.
Picture a city council member saying, "We should add a crosswalk at the corner of the park. Kids cross there every afternoon, and drivers speed through that stretch." That's more than a claim. It's a claim with reasons attached, offered to get the council to agree.
So here's the definition. An argument is a set of claims in which one or more, the premises, are offered as reasons to accept another, the conclusion. 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.
In the crosswalk case, the conclusion is that the council should add a crosswalk. The premises are that kids cross there every afternoon and that drivers speed through that stretch.
Notice what an argument is not. It's not a fight. Two people can calmly trade arguments over coffee, and one angry person can shout for an hour without making a single argument. An argument is a structure: reasons pointing at a conclusion.
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. "The printer jammed twice yesterday, and the technician replaced a roller" is a report. An unsupported assertion is a claim stated with no reason offered for accepting it. "This new scheduling app is a disaster" might be true, but nothing is offered to show it, so it's not an argument.
One more trap. A long paragraph can hold two arguments, not one. A gym flyer might argue that the morning class suits beginners because it's less crowded, and then, in a separate breath, argue that you should try the new rowing machines because they're quieter. Two conclusions, two arguments. Count the conclusions before you assume there's only one.
Pause and try this. A message to a print shop team says, "We should move the weekly meeting to the morning, since three of the five staff members leave by noon." Is that an argument, a report, or an unsupported assertion?
Look for a reason that's offered to support something.
Here's the answer. It's an argument, because the staff schedule is offered as a reason to accept the conclusion that the meeting should move.
No reason offered, no argument.
4. Arguments and explanations
Now for the distinction that trips up almost everyone at first. Listen to two sentences about a soccer game.
"The game was canceled because the field flooded."
"The game will be canceled, because the field is flooding."
Both use "because." Both mention a field and a canceled game. But they're doing different jobs. In the first, everyone already knows the game was canceled. The sentence tells you why it happened. In the second, nobody has announced anything yet. The speaker is giving you a reason to expect the cancellation.
The first sentence explains. The second 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.
Here's the one test I want you to carry. Ask: 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.
Let me give you a picture to hold onto. An explanation is a museum label. The painting is already on the wall, and the label tells you how it got there. An argument is a sales pitch. The product isn't yours yet, and the pitch is trying to change that.
Try the test on a few more. A weather report says flights were delayed this morning because fog covered the airport. The delays already happened, so that explains. A coach tells the team they'll lose the next match unless they fix their passing, because the other side presses hard. The loss hasn't happened, so that argues. A trainer tells a client their legs are sore because yesterday's workout was their first in a month. The client already feels the soreness, so that explains.
One honest caution. Some sentences sit right on the line, and the audience decides. "The store closed because the rent went up" explains to someone who knows the store closed. It argues to someone who thinks the owner retired by choice. When a case is borderline, say which audience you have in mind and why.
Pause and try this. A friend texts, "The bakery on the corner closed because the owner moved away." For a reader who already knows the bakery closed, is that an argument or an explanation?
Ask what the reader already accepts.
Here's the answer. It's an explanation, because the closing is already accepted and the sentence tells why it happened rather than trying to convince anyone of it.
Explanations answer "why is it so?" Arguments answer "why believe it?"
5. Indicator words
Writers often leave little 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 called 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.
These help. But here's the catch, and it has two parts. First, "because" also introduces explanations, as we heard with the flooded field. Second, many arguments carry no indicator at all.
Here's one with none. 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." There's no "so" and no "because." So how do you find the conclusion? You ask one question: what is the writer trying to get me to accept, and what's offered as the reason? The writer wants you to use cold butter. That's the conclusion, and it's the very first sentence. The two sentences after it are the premises.
And watch for indicator words that aren't indicators at all. "Since the new bridge opened, traffic downtown has been lighter." Here "since" means "from the time when." Nothing is offered as a reason, so that's a report, not an argument.
Think of indicator words like footprints in snow. They usually mean someone walked that way, but not always, and some walkers leave none. Use them as clues, then check.
Pause and try this. Does the word "because" in "the game was canceled because the field flooded" mark a premise of an argument?
Recall what the audience already knows about the game.
Here's the answer. No, it introduces an explanation, because the cancellation is already accepted and the sentence says why it happened.
Indicators are clues, not proof.
6. The running question
Every week in this course, you'll run that week's test on one shared argument. We call it the running question: should the campus library stay open around the clock during finals week? It's an illustrative question. The newsletter I'm about to read has no real author, and the course takes no side on the answer.
Here's the passage, from an imagined campus newsletter. "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."
Let's find the parts together. Start with the conclusion. Ask what the writer wants you to accept. It's the first sentence: the library should stay open around the clock during finals week. It comes first, and there's no "so" or "therefore" in front of it.
Now the reasons. A stated reason is a premise that a passage says out loud, as opposed to one the reader has to supply. The first stated reason is that during finals week many students need a quiet, safe place to study late at night. The second is that the library is the only quiet, safe, well-lit study space on campus large enough to meet that need. The third is the cost: about 1,600 dollars in staff wages.
So there's one conclusion and three stated reasons, which makes four claims in all.
Let's check the one figure the passage gives, because careful readers check numbers. The 1,600 dollars comes from two staff members working eight hours a night, for five nights, at 20 dollars an hour. Two staff times eight hours is 16 staff hours a night. Then 16 hours a night times five nights is 80 staff hours. And 80 hours times 20 dollars an hour is 1,600 dollars. The figure checks out.
Last question: argument or explanation? The overnight hours are a proposal. Nobody has agreed to them yet. They're in doubt for the newsletter's readers, so the passage argues.
Now notice what you did not do. You didn't decide whether 1,600 dollars is a lot or a little. You didn't decide whether students should study all night. Finding an argument is not judging it, and it's 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.
Pause and try this. How many stated reasons does the newsletter passage give, and which sentence is the conclusion?
Count the sentences that are offered in support.
Here's the answer. It gives three stated reasons, and the conclusion is the first sentence, because that's the claim the other three are offered to support.
Find the argument first, and judge it later.
Closing
Let me pull it together. Critical thinking is three questions: what is claimed, what supports it, and how good that support is. A claim is a sentence that's true or false, and an opinion is still a claim whose reasons can be judged. An argument offers premises as reasons for a conclusion, which sets it apart from a report and from an unsupported assertion. An explanation tells why something already accepted is so, and the doubt test tells the two apart. Indicator words are clues, not proof. And the running question's passage has one conclusion and three stated reasons.
Next in this module come the slide deck, the Readings and Resources page, the lecture tutorial, the practice set, and the quiz. Then, in Week 2, Analyzing Arguments, you'll write the premises and conclusion you found in a numbered layout, and you'll learn how to supply a reason the writer left unsaid.
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