Here is a complete paragraph from a student essay: "Schools should start later. A sleep researcher said teenagers' body clocks shift two hours later at puberty. Also, my friend falls asleep in first period." It has a claim and two pieces of evidence, and it still doesn't argue anything, because the writer never says how a body clock or a sleeping friend proves that schools should change. The reasoning exists only in the writer's head, and getting it onto the page takes two things: sentences that connect evidence to the claim, and an order of sentences and paragraphs that a reader can follow.
Commentary: the sentences that make evidence count
Topic 1.4 covered writing a claim and choosing evidence for it. Commentary is everything else in a body paragraph: the sentences in your own voice that explain how and why the evidence supports the claim. Evidence shows a reader something; commentary tells them what it means for your argument.
Good commentary does at least one of these things:
- Points to the part of the evidence that matters. Not "this shows sleep is important," but "a two-hour shift means a student woken at 6:30 a.m. for a 7:30 bell is, by her own body's clock, getting up at what feels like 4:30."
- Draws the inference. It says what follows from the evidence: "So the problem isn't discipline; it is biology working against the bell schedule."
- Links back to the claim. It ends where the paragraph's claim begins, so a reader sees the loop close: "A start time that ignores this shift asks students to learn during the hours their brains are least ready to."
Two tests tell you whether a sentence is commentary or filler. First, could it be written without having seen the evidence? "This shows how important sleep is" could, so it isn't explaining anything. Second, does it add an idea the evidence alone didn't state? A sentence that restates the quotation in other words is summary, not commentary, and on the essay it earns nothing.
A useful ratio for timed writing: for each piece of evidence, write at least as many sentences of commentary as you used to present the evidence. That is a habit, not a rule of scoring, but it guards against evidence stacked on evidence with no explanation between.
Ordering a paragraph so the reasoning shows
A body paragraph has a job: to defend one claim that moves your argument forward. The order that does this most clearly is:
- The claim (topic sentence), stated so it is debatable and connected to the thesis.
- A setup, when needed: one sentence that tells the reader what to look for in the evidence or why it is relevant.
- The evidence, introduced and, if quoted, worked into your own sentence.
- Commentary on that evidence.
- More evidence and commentary if the claim needs them, then a final sentence that ties the paragraph to the thesis.
The setup sentence is easy to skip and often decides whether a reader understands the example that follows. If your evidence is a story about a homeowner who needs a tile saw once, the sentence before it should establish the pattern the story illustrates ("most tools are used a handful of times and then stored for years"). Then the story arrives as proof of something the reader is already looking for. Revision questions on the exam ask exactly this: which version of a sentence best "sets up" or "introduces" the example in the next sentence.
When a paragraph has two pieces of evidence, put the one that needs less explanation first and the stronger or more surprising one second, so the commentary builds instead of starting over. And each piece of evidence must serve this paragraph's claim. A true, interesting fact that supports a different claim belongs in a different paragraph or nowhere.
Ordering paragraphs: building a line of reasoning
Topic 1.5 showed how to read a line of reasoning, the chain of claims that leads to a thesis. Writing one means deciding what your reader must accept first. Three questions settle the order of your paragraphs:
- Does one claim depend on another? If your second point only makes sense once the first is granted, the order is fixed. An argument that a trail would be cheap to build ("the old rail bed is already graded") makes more sense after the reader has accepted that the trail is worth building at all.
- Where is your strongest point? Many writers put it last, so the argument ends at full strength. Some put it first, when the audience is impatient or skeptical and needs a reason to keep reading. Either is defensible; a random order is not.
- Where does the objection go? An answer to the opposing side usually comes after your own case, when readers have reasons to weigh against the objection, and before your conclusion.
Each paragraph's opening sentence should show how it advances the thesis, not merely announce a new subject. "Another reason is cost" tells the reader a list is continuing. "Even a reader unmoved by the health argument should notice what the trail would cost: almost nothing" shows the relationship between this claim and the last one. Transitions between ideas are covered in depth in Unit 5; for now, aim for topic sentences that make the logic between paragraphs explicit.
Worked examples
A student is arguing that teachers should allow each student to retake one test per semester. Revise this paragraph so its reasoning is on the page.
Retakes help students learn. In my chemistry class last year, I failed the stoichiometry test. Then I retook it and got an 88. Also, many colleges allow students to retake courses.
Show solution
What's wrong. There is a claim and two pieces of evidence, but no commentary. A reader can't tell how a higher second score shows learning (maybe the student just saw the questions twice), and the college evidence supports a different claim (that retakes are normal) without saying so.
Revision.
A retake gives a student a reason to learn material that a single test would have let them abandon. When I failed my chemistry test on stoichiometry last year, my first instinct was to accept the grade and move on to the next unit, even though every later unit, from gas laws to titration, depended on it. The retake policy changed that calculation: to raise the grade, I had to go back and actually understand mole ratios, and I scored an 88 on a new version of the test. The second score mattered less than what it required. Without the chance to retake, the cheapest path would have been to keep failing quietly at the skill the rest of the course was built on.
Why it works. The claim now states a mechanism (retakes give a reason to learn), which the evidence can prove. The detail "a new version of the test" heads off the objection that the student memorized answers. The commentary ("the retake policy changed that calculation," "the second score mattered less than what it required") explains the evidence instead of repeating it. The college fact is gone: it supported a different claim and would have pulled the paragraph off course.
A student is writing a letter to a county board arguing that an abandoned rail line should become a walking and biking trail. The board has expressed concern about cost, and some members have heard complaints from landowners along the line. The student has three body paragraphs:
- A: The rail bed is already flat and graded, so building the trail would cost far less than a new path.
- B: Nearby residents have no safe place to walk or bike; the county roads have no shoulders.
- C: Landowners worry about privacy and trespassing; trails elsewhere have handled this with fencing and posted hours.
Choose an order and justify it.
Show solution
Order: B, A, C.
B first because the other claims depend on it: cost only matters once the board agrees there is a need worth paying for. Leading with the need also gives the board a reason to keep reading a letter about spending.
A second because it answers the board's stated concern right after the need is established, so "this is cheap" reads as good news about something they now want, not as a sales pitch for something they don't.
C last because it is an objection, and it is best answered after the reader has reasons to weigh against it. Placing it last also lets the letter end with a solution (fencing and hours), not with a worry.
A different order could be defended (for a board obsessed with cost, A could come first to keep their attention), but the justification must rest on what this audience needs to accept and in what order. "I put my best reason last" without saying why it is best for this board is not a justification.
The passage below is a draft.
(1) When the Millbrook Public Library began lending tools in 2019, most residents expected the program to be a novelty. (2) Five years later, the tool collection is the busiest section of the library on weekends. (3) Its 400 items range from ladders and drills to a pressure washer and a sewing machine. (4) Many people own tools of their own. (5) A homeowner who needs a tile saw once, to redo a bathroom floor, would spend more than $300 to buy one; borrowing it costs nothing. (6) The library also offers Saturday classes on basic repairs. (7) A tool library, in other words, turns objects that would sit unused in garages into equipment a whole town can share.
Question 1. In sentence 4 (reproduced below), the writer wants to set up the example in sentence 5.
Many people own tools of their own.
Which version best accomplishes this goal?
- (A) (as it is now)
- (B) Most household tools are used only a few times before they are stored for good.
- (C) Tools have become more expensive in recent years.
- (D) Two volunteers repair the library's broken tools each week.
Question 2. The writer is considering adding the following sentence after sentence 5.
Multiply that by every household on a street, and one shared saw replaces dozens of purchases that would have sat in garages.
Should the writer add this sentence?
- (A) Yes, because it explains how the single example in sentence 5 supports the idea of sharing that sentence 7 states.
- (B) Yes, because it provides a statistic about the number of saws in the town.
- (C) No, because it repeats the information in sentence 5.
- (D) No, because it shifts the focus from the library to individual homeowners.
Show solution
1. (B). Sentence 5 is an example of a tool needed once and then not again. Choice B states that general pattern, so the tile saw arrives as proof of it, and B also prepares sentence 7's "objects that would sit unused." (A) works against the line of reasoning: owning tools doesn't lead to an example about borrowing one. (C) is the tempting choice because sentence 5 mentions a price, but cost alone is not what the example illustrates; the point is that the saw is needed once. (D) is true-sounding but unrelated to sentence 5.
2. (A). Sentence 5 shows one homeowner saving money; sentence 7 claims a whole town shares resources. The new sentence is commentary that bridges the two, scaling one case up to a street. (B) misdescribes it: "dozens" is not a statistic about the town. (C) is wrong because the sentence adds the step from one household to many. (D) is wrong because the sentence moves toward the library's role, not away from it. The general move: when a revision question asks whether to add a sentence, decide what job that sentence would do (evidence, commentary, setup) and whether the paragraph's reasoning is missing that job at that spot.
Prompt: Many schools fill every period of the day with scheduled classes and activities. Write an argument about whether high schools should build unscheduled free time into the school day. Write one body paragraph, with a claim, evidence and commentary, that would fit in your essay.
Show solution
Model paragraph.
Unscheduled time is where students practice the skill school says it values most: deciding for themselves what to work on. A fully scheduled day makes every choice for students, from when to read to when to eat, and then expects them to manage their own time the moment they reach college or a job. At my school, juniors get one free period on Wednesdays, and the library during that hour looks nothing like it does during class: one group rehearses a debate case, two students argue over a chemistry problem nobody assigned, and a few people sleep. The sleepers are the point, not an objection to it. A sixteen-year-old who wastes a free hour and notices the cost on Thursday is learning, at low stakes, what a college freshman learns at the price of a failed semester. Schools that never give students time to misuse will graduate students who have never learned to use it.
Why it earns credit. The first sentence is a debatable claim tied to a larger thesis (schools should build in free time). The second sentence is a setup: it names the contradiction the evidence will expose. The evidence is a specific personal observation with concrete details. The commentary does real work: it turns the obvious objection (some students waste the time) into support, and the final sentence connects the observation back to the claim. A paragraph that said "Free time is good because students can relax and study. At my school we have a free period and people use it well" would have a claim and evidence but almost no reasoning, and scorers would place it low on the evidence-and-commentary row.
Where students lose points
On the exam
The argument essay is scored on a thesis (one point), evidence and commentary (up to four points), and sophistication (one point). The middle row is where reasoning and organization matter most: the top scores go to essays whose commentary explains how each piece of evidence supports a line of reasoning, while essays that summarize or list evidence score lower however much they include. In the multiple-choice section, revision questions on a numbered draft test the same skill: whether to add or delete a sentence, which version best sets up an example, and where a sentence belongs.
Check yourself
Question 1
A student's paragraph claims that cities should plant more street trees. After citing a study that tree-lined streets were 5 degrees cooler on summer afternoons, which sentence is the strongest commentary?
- A
This study shows that streets with trees were cooler.
- B
Trees are also beautiful and make neighborhoods more pleasant.
- C
On the hottest days, five degrees can decide whether an older resident without air conditioning can safely walk to the bus stop, which makes shade a public health measure, not decoration.
- D
Many other studies have also been done on this topic.
Show answer
C
C says what the number means for people and connects it to a reason the city should act. A only restates the evidence (summary), B adds a new, unsupported claim, and D adds nothing to the reasoning.
- A
Question 2
A student arguing that the school should open its gym to the public on weekends has three paragraphs: (1) local children have no indoor place to play in winter; (2) the gym already sits empty on weekends, so opening it costs only a supervisor's wages; (3) some parents worry about damage, which a sign-in system and a deposit would handle. Why is (1), (2), (3) a sound order?
Show answer
The need comes first because the cost argument only matters once the reader accepts there is a need worth paying for. The low cost follows as an answer to the obvious next question, and the objection comes last, after the reader has reasons to weigh against it, so the argument ends on a solution.
A justified order rests on dependence (what the reader must accept first) and on where an objection is best answered, not on the order the writer thought of the points.
Question 3
In a draft about a community fridge, sentence 3 reads: "The fridge is behind the laundromat on Pine Street." The writer wants this sentence to set up sentence 4: "One morning in March, a restaurant left forty unsold sandwiches; by noon every one had been taken." Which revision of sentence 3 best does this?
- A
The fridge was painted by students from the high school.
- B
Food that would have been thrown away often goes to people who need it within hours.
- C
The laundromat's owner pays for the fridge's electricity.
- D
Restaurants in the area serve many kinds of food.
Show answer
B
Sentence 4 shows surplus food reaching people quickly, and B states that general pattern, so the sandwiches arrive as proof of it. D is the tempting distractor because it mentions restaurants, but it doesn't name the idea the example illustrates.
- A
Question 4
A paragraph claims that a town's new bike lanes made downtown safer. It cites the drop in crashes, then cites a survey showing riders like the lanes' green paint. What should the writer do with the survey, and why?
- A
Keep it, because more evidence always strengthens a paragraph
- B
Move it before the crash data, because weaker evidence should come first
- C
Cut it or move it to a paragraph about popularity, because riders liking the paint does not show the lanes made downtown safer
- D
Keep it and add a quotation from a rider, because personal testimony is the strongest evidence
Show answer
C
Evidence must support the paragraph's claim. A preference for the paint is about appeal, not safety, so it breaks the line of reasoning. Choice A is the tempting mistake: piling on evidence that serves a different claim weakens the paragraph.
- A