Delineate and evaluate the argument in an op-ed: sound reasoning, relevant and sufficient evidence, and irrelevant evidence

Learning goal: Delineate and evaluate the argument and specific claims in a text, assessing whether the reasoning is sound and the evidence is relevant and sufficient, recognize when irrelevant evidence is introduced, and cite the textual evidence that most strongly supports each assessment.

Original op-ed — Fill It In and Move On. A letter to the invented Millbrook newsletter, dated April 2026, by an invented resident, Carl Brandt. It responds to the same hypothetical feasibility study as the companion article; its figures and stories are fictional.

I have lived on Towpath Street for forty-one years, and in all that time the feeder canal behind my house has held nothing but leaves, shopping carts and, one memorable August, a deer. Now the Historical Society wants the council to spend millions turning that ditch into a "heritage waterway." The council should fill it in, pave the trail and move on.

Start with the money. The Society likes to say the state will pay 60 percent. What it does not say is that the grant pays for construction only. The feasibility study puts the town's annual operating bill at $140,000 — every year, forever. That is two full-time police officers, or the entire summer recreation program, or a decade of pothole repairs. A cost that repeats every year should be compared with other costs that repeat every year, not with a one-time grant that arrives once and disappears. Counting the years, the real price of this project is at least $5 million.

Then there is the council's record. Two years ago the same council approved a parking garage that came in $300,000 over budget. Are these the people we trust with a canal?

The Society will tell you about the kayak club. I have nothing against kayaks, but 140 people pledging "volunteer labor" is not the same as 140 people showing up in February to chip ice off a lock gate. Ask any coach how many parents volunteer in September and how many are left in May.

And who is this for? Nobody under thirty cares about canals. The Society's president moved here from Columbus in 2009. My grandfather, who worked at the elevator, used to say the canal smelled like a swamp every summer it had water in it. That was the 1920s. The canal has been dry for eighty years, and if the town had needed it, somebody would have noticed by now.

Finally, consider where this ends. Restore the canal, and next year someone will want the mill restored, then the depot, then the streetcar line. A town cannot rebuild its entire nineteenth century on a budget written in the twenty-first.

I am not against history. I am against paying $140,000 a year for a museum you can fall into. Fill it in, plant some trees along the trail and put the marker back where people can read it.

Delineating the argument. To delineate an argument is to lay it out: the main claim, each reason offered for it, and the evidence offered for each reason, in the order the text gives them. Do this before evaluating anything, because a judgment about an argument no one has mapped is a judgment about an impression. The op-ed's main claim is stated in the first paragraph: the council should fill the canal in and pave the trail. It offers five reasons. Reason 1, cost: evidence is the study's $140,000 yearly operating figure, three comparisons (two officers, the recreation program, a decade of potholes) and a total of "at least $5 million." Reason 2, the council cannot be trusted with a big project: evidence is a parking garage $300,000 over budget. Reason 3, volunteer pledges are unreliable: evidence is an analogy to sports parents. Reason 4, nobody needs the canal: evidence is the claim that nobody under thirty cares, the Society president's arrival from Columbus in 2009, a grandfather's memory of summer smell in the 1920s and eighty dry years. Reason 5, restoring the canal leads to restoring everything: no evidence, a predicted chain of events. The map is the delineation; the evaluation comes next, one reason at a time.

What sound reasoning means. Reasoning is sound when the conclusion actually follows from the reasons and the reasons are true or well supported. Both conditions matter. A conclusion can fail to follow from true statements, and a conclusion can follow perfectly from a false one. The op-ed contains a genuinely sound piece of reasoning in paragraph 2: "A cost that repeats every year should be compared with other costs that repeat every year, not with a one-time grant that arrives once and disappears." Read as a principle about comparison, put costs on the same time basis before weighing them, it is correct, and it is the point the companion article makes when it converts both options to twenty-year totals. Its wording, "not with a one-time grant," is narrower than the principle: a one-time amount can be compared with a yearly one once both are expressed over the same period. A reader evaluating the op-ed should say so; evaluation is not fault-finding, and an argument's strongest reasoning must be credited before its weakest is exposed.

Paragraph 5 contains reasoning that is not sound: "The canal has been dry for eighty years, and if the town had needed it, somebody would have noticed by now." The conclusion, that the town does not need it, does not follow from the premise that it has been dry. A thing can go unused because it is unavailable, not because it is unwanted; nobody noticed needing the canal for the same reason nobody notices needing a bridge that does not exist. Paragraph 6 is a second unsound pattern, often called a slippery slope: it asserts that one restoration will cause a chain of others (mill, depot, streetcar) without evidence that any such chain has begun or that the council could not stop it. Predicting a chain is not evidence of the chain.

Relevant and sufficient evidence. Evidence is relevant when it bears on the claim it is offered for. Evidence is sufficient when there is enough of it, of the right kind, to justify the strength of the claim. The two are separate tests, and evidence can pass one while failing the other. The $140,000 figure is relevant to the cost reason and, since it comes from the feasibility study, well sourced. The three comparisons are relevant too; they translate a figure into things a reader values, which is legitimate as long as the reader remembers that each is an alternative use, not a consequence. Two limits remain: none of the three is sourced (the op-ed gives no salary, program budget or repair figure), and the third sets one year's upkeep against "a decade of pothole repairs," mixing time bases in the way the op-ed's own principle warns against. The claim that the "real price" is "at least $5 million" is a different matter. The study's twenty-year figure for the town is $4.24 million; the op-ed gives no source, no time span and no calculation for $5 million. As written it is unsupported: it might be true over a longer horizon, but the reader is not told, so the evidence for that specific claim is insufficient. The garage overrun in paragraph 3 is relevant to the reason it is offered for, that the council cannot be trusted with a big project, because a past overrun bears on how a council manages money; but one project with no cause given (a contractor's error and a council's carelessness look the same in a total) is insufficient for a general claim about the council, and the reason itself reaches the main claim only through a further step the op-ed never takes: that a canal is harder to manage than a trail.

The grandfather's memory is relevant to a claim about how the canal smelled in the 1920s. It is not sufficient for a claim about a modern restoration whose budget includes water-quality testing, because one recollection from a century ago says nothing about a dredged, tested channel. "Nobody under thirty cares about canals" is offered without any evidence; it is an assertion presented as evidence, and the reader should mark it as such rather than treat it as refuted or confirmed. The coach analogy for volunteers is relevant and reasonable as a caution, but an analogy is not a measurement; it makes the claim plausible without establishing how many of the 140 members would actually turn up, so it is suggestive rather than sufficient.

Recognizing when irrelevant evidence is introduced. Irrelevant evidence is evidence that bears on some other claim than the one being argued. It is often introduced with a transition that changes the subject while keeping the tone of argument, and it works on readers because it is true. Paragraph 5 is the case here: "The Society's president moved here from Columbus in 2009." The sentence sits under the question "who is this for?", it is stated as a plain fact, and within the fiction it may well be accurate. Apply the relevance test: if the president had been born in Millbrook, would the town need the canal any more or less? No. Where the Society's president grew up has no bearing on whether the canal is needed, so the evidence is irrelevant to the claim it is placed under; what it does is invite the reader to feel that restoration is an outsider's idea. Notice the subtlety: the same fact would be relevant to a different claim, such as "the Society's leadership does not speak for long-time residents," though even there it would be one fact about one person. Relevance is a relationship between a piece of evidence and a particular claim, which is why delineating the claims first is essential. Compare the garage overrun in paragraph 3, which students often call irrelevant: it does bear on the claim it is offered for, the council's competence, and fails on sufficiency instead. An evaluator who has not separated the claims cannot tell irrelevant evidence from insufficient.

Evaluating the whole. The argument's strongest parts are the recurring-cost principle and the caution about volunteer pledges, both relevant and one of them sound as reasoning. Its weakest parts are the unsourced $5 million, the irrelevant remark about where the Society's president came from, the single garage overrun asked to carry a general claim, the unsound inference from eighty dry years and the unsupported slippery slope. A fair evaluation says both. It also notes that "a museum you can fall into" is vivid rhetoric, not evidence; it makes the reader smile, and it is exactly the kind of sentence a careful reader sets aside when assessing whether the claims are supported.

Worked delineation: Main claim: fill the canal and pave the trail. Reason 1: the recurring cost is large. Evidence: $140,000 a year from the study; three comparisons; "at least $5 million." Reason 2: the council cannot be trusted with a big project. Evidence: one garage overrun. Reason 3: volunteers will not last. Evidence: the sports-parent analogy. Reason 4: the canal is not needed. Evidence: nobody under thirty cares; the president moved from Columbus in 2009; grandfather's memory; eighty dry years. Reason 5: restoration will not stop at the canal. Evidence: none; a predicted chain. Laying it out this way already shows that Reason 5 rests on nothing and that Reason 2 rests on a single case.

Worked relevance test: Take the sentence about the Society's president and ask the counterfactual question: had she been born in Millbrook, would the town need the canal any more or less? Neither. The fact does not move the claim it is placed under, so it is irrelevant to it. Now attach the same fact to a different claim, "the Society's leadership does not speak for long-time residents," and ask again: does where she came from bear on that? Somewhat, as one fact about one person. The fact is unchanged; its relevance changed with the claim. Run the same test on the garage overrun: had the garage come in under budget, would "the council cannot be trusted with a big project" be weaker? Yes, so the overrun is relevant to that reason; its problem is that one overrun with no stated cause cannot carry a claim about the council in general.

Worked sufficiency assessment: Claim: the canal is not needed. Evidence offered: one relative's memory of summer smell about a century ago, an unsupported statement about people under thirty, an irrelevant fact about where the Society's president came from, and eighty dry years. The memory is relevant only to an old condition and says nothing about a dredged, tested channel; the statement about age has no evidence at all; the dry years do not show lack of need, as the reasoning section explains. Four pieces of evidence, none sufficient and one irrelevant, and together still insufficient, because quantity does not repair relevance. Compare the cost reason, where one well-sourced figure is sufficient for the modest claim that the cost is large.

Argument map with verdicts: Draw the op-ed as a tree: the main claim at the top, five reasons beneath it, the evidence beneath each reason. Beside each piece of evidence write three verdicts: relevant to this reason or not, sufficient for this reason or not, and sourced or not. Beside each reason write whether the reasoning from evidence to reason is sound. Circle every piece of evidence that is irrelevant, write the question or transition it was placed under and the different claim it would be relevant to, and mark separately any evidence that is relevant but insufficient.

Independent performance: Write a four-paragraph evaluation of the op-ed. Paragraph one delineates the argument in your own words. Paragraph two identifies the soundest reasoning in the text and explains why it is sound, citing the sentence. Paragraph three identifies one unsound inference and one piece of irrelevant evidence, explains the test that exposes each, and states what different claim the irrelevant evidence would support. Paragraph four assesses whether the evidence for the "not needed" reason is sufficient and gives an overall judgment of the argument that credits its strengths. Success criteria: every verdict cites the sentence it judges; relevance and sufficiency are assessed separately; the $5 million claim is compared with the study's $4.24 million and judged as unsupported rather than as false; and the evaluation names at least one strength before any weakness.