Week 2 — Shape First: Keying and Testing Arguments — Traditional alternative (no AI)

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 2 of the term — put arguments in standard form, key them for validity, break an invalid form with a counterexample, read an argument charitably, and explain the difference between valid and true to someone new to philosophy.

This week you learned how arguments work: standard form, validity and soundness, the valid and invalid forms, counterexamples, inductive strength, thought experiments, and reading charitably. Last week you learned what philosophy is and the Socratic habit of testing a definition with a counterexample. This week's lecture tutorial, quiz, discussion, and Philosophy Workshop practice the same ideas from other angles; this assignment is where you put them together.

The task

You will use Dataset B, the argument set (illustrative), from this week's chapter. Its premises are written for teaching and are not claims the course endorses. The course keys its arguments for validity only, never for soundness, because the premises are open questions. You will also use two everyday arguments written for this assignment; they are illustrative and describe no real person or place.

Part A — reconstruct and key four arguments. Here are the four arguments:

1. Dataset B, argument 3: "If an act maximizes happiness, it is right. If it is right, we ought to do it. So if an act maximizes happiness, we ought to do it."
2. Dataset B, argument 8: "If a machine understands Chinese, it can answer questions in Chinese. This machine answers questions in Chinese. So it understands Chinese."
3. A ferry dispatcher: "If the wind is above the safe limit, the ferry is cancelled. The ferry is cancelled. So the wind is above the safe limit."
4. A pharmacy clerk: "Either the prescription was sent to this store or it was sent to the downtown store. It was not sent to this store. So it was sent to the downtown store."

For each one, write it in standard form (P1, P2, then C introduced by "So"), say what P, Q, and R stand for, name its form, and say whether it is valid or invalid, with a one-sentence reason that uses the definition of validity. Then work this problem, showing your reasoning:

1. Dataset B, the argument set (illustrative), holds 10 arguments, and 6 of them are keyed valid. How many are keyed invalid?

Part B — test and read charitably. Work this problem first, showing your reasoning:

1. Of the 6 valid arguments in Dataset B, 2 are modus ponens. How many of the valid arguments use one of the other valid forms?

Then do three things:

• Counterexample. Build a counterexample to the form of the ferry dispatcher's argument: keep the exact form, use everyday content anyone can check, and show that the premises are true and the conclusion false. End with one plain sentence saying what the counterexample shows.
• Charitable reading. At a community garden meeting, a volunteer says, "We should stop holding the weekend workdays, because hardly anyone comes." Restate the volunteer's argument in its strongest form, in standard form, with any premise you add marked "(added)".
• Objection and reply. Give the strongest objection you can to one premise of your charitable version, then a reply from the volunteer's side. End with one plain sentence naming where the two sides disagree.

Explain it to a non-expert

A roommate who has never taken philosophy reads argument 3 of Dataset B and says, "That argument is valid, so it must be true." Write a 3–5 sentence message in everyday words that explains what valid means, why a valid argument can still have a false premise, and one honest limit of what a validity check can tell anyone. Explain any term your roommate might not know.

For a different, ungraded example, imagine a coworker who asks why a sales forecast built on three strong months is not a guarantee. Model answer: "The forecast is a good bet, not a promise. Philosophers call it an inductive argument: past months make the next month likely, but they cannot lock it in. The more months, and the more typical they were, the stronger the bet gets. One limit: even a strong bet can lose if something new happens, like a store closing nearby."

Use that pattern for your message to your roommate, with your own explanation of valid and true.

Revise and reflect

Put your first draft away for a few hours, then reread it against Chapter 2. For each reconstruction, underline the premise that matches P and the one that matches Q, and check the form's name against the chapter's list; for the counterexample, tick that its form matches the ferry argument line for line and that its premises are true and its conclusion false; and check that your roommate message separates valid from true. Make at least one change and keep both versions. Then answer one of these two options in 2–4 sentences; they carry the same weight:

• (a) Which change made one of your reconstructions or form names more exact, and which definition showed you it was needed?
• (b) Which change made your counterexample or your charitable reading stronger, and what had you missed at first?

Deliverables

Submit one document or recording that contains, in this order:

• your Part A reconstructions with their forms, keys, and reasons, and your count of the invalid arguments in Dataset B;
• your Part B count of the other valid forms, your counterexample, your charitable reading, and your objection and reply;
• your message to your roommate;
• your first and revised versions of the part you changed, and your reflection.

Choose how you show it. Present your work as written text, or as a recorded audio or video explanation of about five minutes with a transcript. Every form is graded by the same scoring criteria. Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

This version is designed to be completed without AI: do the reconstructions, the counterexample, the charitable reading, and the writing yourself, without a chatbot or other AI tool. Submitting AI-generated work as your own, or copying another student's work, is an integrity violation under the course policy.

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