Week 7 Philosophy Workshop: The Harbor Ferry and the Fog Crossing

Part 1 — The Big Picture

This week you learned what it means for a thing to stay the same over time, tested it on Plutarch's ship of Theseus and Locke's memory theory, met the Buddhist teaching of no-self, and compared hard determinism, libertarianism, and compatibilism, with Frankfurt's challenge to the principle of alternate possibilities. In this workshop you take one illustrative packet from a small harbor town arguing about its old ferry and the pilot who crossed in the fog. You reconstruct four short arguments and key each for validity. Then you test a variation of the ship of Theseus, the overnight ferry, and ask whether replacing every plank at once changes your answer. You write a short dialogue between a hard determinist and a compatibilist about the fog crossing, each in their strongest form. Last, you check a chatbot's version of the same work and correct its slips by hand, starting with whose English words the ship's famous line really is.

Time budget: Plan for about 90 minutes.

Part 2 — The Task

Guiding question: Which of the harbor's four arguments are valid, which one runs a conditional backward, does replacing every plank in one night change whether the ferry is the same ferry, and is the pilot responsible for the fog crossing?

Workshop data: Harbor ferry packet: four illustrative arguments and two thought-experiment variations, of the ship of Theseus and of Frankfurt's cases

Source: An illustrative packet of four short arguments and two thought-experiment variations written for this course's workshop; it describes no real harbor or person, and its premises are written for teaching, not claims the course endorses.

• Rows: 4 arguments (A1 to A4) and 2 thought-experiment variations; the reconstruction table has 4 rows and the overnight-ferry table has 4
• Arguments: A1 the ferry's planks; A2 the pilot who could not have done otherwise; A3 the pilot's caused choice; A4 the remembered crossing
• Thought-experiment variations: the overnight ferry, labelled as a variation of Plutarch's ship of Theseus; and the fog crossing, labelled as a variation on the shape of Frankfurt's cases

Part 3 — Materials & Procedure

Tools and materials

• A free word processor or note-taking app for arguments in standard form and short dialogues, with the pinned public-domain texts on Project Gutenberg and the Internet Classics Archive open beside it; and one approved chatbot used as a sparring partner whose reconstructions, quotations, and attributions the student checks word for word against the pinned text and record before trusting them
• A free word processor or note-taking app
• One approved chatbot

Ways of working

• reconstruct-the-argument
• test-the-thought-experiment
• write-the-dialogue

Procedure

1. Read the harbor ferry packet in Part 2 twice. In your notes, copy each of A1 to A4 into standard form: number the premises P1 and P2, and write the conclusion last as C, introduced by So. Tool: A free word processor or note-taking app. Check: Four reconstructions, each with numbered premises and one conclusion line that begins with So.
2. In the first table, name the form of each argument and write valid or invalid with a one-sentence reason that uses the definition of validity. Then name the premise a defender of the other side would reject, without calling any argument sound or unsound. Tool: A free word processor or note-taking app. Check: Every row of the first table has a form, a key, a reason, and a rejected premise; no row says sound or unsound.
3. Count the arguments in the second table: how many are valid and how many are invalid. Show the subtraction from the 4 arguments in the packet. Check: A count of valid and invalid arguments, with the subtraction shown.
4. Work the overnight ferry in the third table: give the 'same ferry' answer and the 'new ferry' answer for the overnight case, say whether the overnight change pulls your intuition differently from Plutarch's gradual repair, and say which sense of 'same' the question is about. Check: Each row is filled in, and the overnight ferry is labelled as a variation of Plutarch's ship of Theseus.
5. Write a short dialogue of four to six lines between a hard determinist and a compatibilist about whether the pilot is responsible for the fog crossing. Give each speaker their strongest point, have each answer the other, use the fog crossing as a Frankfurt case, and end with one plain sentence naming where they disagree. Tool: A free word processor or note-taking app. Check: Each speaker answers the other, neither is a weakened version, and a closing sentence names the disagreement.
6. Paste the prompt from Part 6 into one approved chatbot after your completed work, read its reply, and write the critique report. Or, on the equivalent route, mark up the printed flawed analysis instead. Tool: One approved chatbot. Check: A report that quotes at least two slips and corrects each by hand against the packet and Chapter 7.

Fallback route

When to use it: Use this route if you cannot open a word processor or a note-taking app.

Copy the three tables by hand onto paper or into any text file, read the packet from this page, write the four reconstructions, the count, the overnight-ferry table, and the dialogue by hand, and complete every analysis question and the critique step in the same order. Submit a photo or scan of the paper, or the text file, for equal credit.

This route earns the same credit as the primary route.

Part 4 — The Scaffold

Key each argument by its form before you think about its premises, so a validity judgment never rests on whether a conclusion sounds true.

Student scaffold table 1

Argument	Form	Valid or invalid	Reason	Premise a defender of the other side rejects
A1 (the ferry's planks)
A2 (the pilot who could not have done otherwise)
A3 (the pilot's caused choice)
A4 (the remembered crossing)

Count the keys so every number you report traces back to the table above.

Student scaffold table 2

Count	Number	How you got it
Arguments in the packet	4	Given in the packet
Valid arguments
Invalid arguments

Run the variation one step at a time, so your answer about the overnight ferry is argued rather than asserted.

Student scaffold table 3

Step	What you find
The 'same ferry' answer for the overnight case
The 'new ferry' answer for the overnight case
Does the overnight change pull your intuition differently from gradual repair, and why?
Which sense of 'same' the question is about

Part 5 — Analysis Questions

1. How many of the packet's 4 arguments are valid, and how many invalid? Show the subtraction, and name the form of each valid one.
2. Why is A3 invalid even if both of its premises are true? Explain with a same-shape argument of your own whose premises are true and whose conclusion is false, and one plain sentence about the pilot.
3. Using your overnight-ferry table, explain whether replacing every plank in one night changes the answer Plutarch's gradual repair invites, and why. Keep the original case credited to Plutarch's Life of Theseus, and quote the course's line only with its translator.
4. In your dialogue, what is the strongest point each speaker makes, and where exactly do they disagree? Connect the fog crossing to A2 and the principle of alternate possibilities. End with one plain sentence.
5. What can a validity check not tell you about A2 or A4, and what can the overnight ferry not show about whether you are the same person you were as a child?
6. Choose one reflection: (a) which argument in the packet did you first key the wrong way, and what in this week's definitions changed your mind? or (b) which speaker in your dialogue did you start out agreeing with, and did your view survive writing the other side at its strongest?

Part 6 — AI-Critique Moment

Choose one equal-credit critique route. Route A: ask an approved AI tool to critique your completed work, then check its response against your own evidence. Route B is the no-AI equivalent printed below.

Approved tools: Claude, Gemini, ChatGPT, Grok, Microsoft Copilot.

Prompt to paste:

I've completed my reconstruction table, my count, my overnight-ferry table, and my short dialogue above. Here is an illustrative workshop packet from my philosophy course. Harbor ferry packet (illustrative): a small harbor town debates its old ferry, whose planks have all been replaced over many years, and the pilot who steered it through fog one night. A1: If the ferry is the same ferry, then it has the same planks. It does not have the same planks. So it is not the same ferry. A2: If the pilot is morally responsible for crossing in the fog, then the pilot could have done otherwise. The pilot could not have done otherwise. So the pilot is not morally responsible for crossing in the fog. A3: If determinism is true, then the pilot's choice has causes. The pilot's choice has causes. So determinism is true. A4: If I remember steering the ferry through the fog, then I am the person who steered it. I remember steering the ferry through the fog. So I am the person who steered it. The overnight ferry (a variation of Plutarch's ship of Theseus, written for this workshop): instead of replacing the planks one at a time over years, a crew replaces every plank in a single night. The fog crossing (a variation on the shape of Frankfurt's cases, written for this workshop): the pilot decided, for reasons of their own, to cross in the fog; unknown to the pilot, the harbor master had planned to order the crossing if the pilot had started to refuse, but never had to. Please do seven things. First, put each of A1 to A4 in standard form, and say whether each is valid and whether it is sound. Second, give me Plutarch's exact words about the ship of Theseus. Third, tell me who first came up with the ship of Theseus and who proposed the memory theory of personal identity. Fourth, tell me when Frankfurt published his paper on alternate possibilities and what it argued. Fifth, explain compatibilism and the Buddhist teaching of no-self, and say whether the self was ever questioned outside Europe. Sixth, the memory theory reminds me of 'I think, therefore I am'; tell me which book that line comes from. Seventh, tell me whether the overnight ferry is the same ferry and whether the pilot was free, and end with a balanced summary.

Test the response for these likely failures:

• Chatbots often call A3 valid, reading 'the choice has causes, so determinism is true' as if it were modus ponens.
• Chatbots often say A2 is sound, or that it proves the pilot is not responsible, without asking whether its first premise is true.
• Chatbots often present an English sentence about the planks as Plutarch's own words, with no translator named.
• Asked for Plutarch's exact words, chatbots often supply a smoother sentence about the ship that appears in no pinned text, or a quotation from Locke about memory.
• Chatbots sometimes credit the ship of Theseus to Locke or to a later philosopher who discussed it, rather than to Plutarch's Life of Theseus.
• Chatbots sometimes date Frankfurt's paper to the 1970s or 1980s, or give it a different title.
• Chatbots often say compatibilists deny determinism, or reduce compatibilism to 'you are free whenever you feel free', and read no-self as the claim that nothing exists.
• Chatbots sometimes say questions about the self began in Europe, or treat the Buddhist teaching as a religious aside rather than philosophy.
• Asked where 'I think, therefore I am' comes from, chatbots usually name the Meditations, often with the year 1641.
• Asked whether the overnight ferry is the same ferry or whether the pilot was free, chatbots often announce one answer as settled.
• Chatbots often end a 'balanced' summary by saying science has shown determinism is true, or that Frankfurt proved compatibilism right.

Write 3-5 sentences naming what the chatbot got right and at least two places where it slipped into one of the failures above, quoting its words and correcting each by hand against the packet and Chapter 7.

Equivalent route (no AI required)

No AI account is required for this workshop. This route assesses the same objectives, Objective 4 (compare positions on the mind-body problem, personal identity, and free will, and evaluate them with the thought experiments that test them) and Objective 2 (identify arguments, put them in standard form, judge whether they are valid, sound, or inductively strong, and test claims with counterexamples and thought experiments), takes comparable effort of about the same 90 minutes, uses the same rubric, and earns the same credit. Instead of the chatbot, critique this flawed analysis of the harbor ferry packet, printed here in full: "A1, A2, A3, and A4 are all valid, and A3 is modus ponens, which proves determinism is true. A2 is sound, so the pilot is not responsible. John Locke invented the ship of Theseus, and Plutarch wrote in English that the old planks were taken away. Locke said in his own words that memory is the soul, quoted here in full. Frankfurt published his paper in 1985 and showed that nobody is ever responsible. Compatibilists deny determinism, and the Buddhist no-self teaching says nothing exists; questions about the self were a European invention. The memory theory is Descartes' idea, from the Meditations, where he wrote 'I think, therefore I am'. The overnight ferry is plainly a new ferry. To sum up fairly, science has proved determinism, so hard determinism is right." Mark every error you find, name the failure it shows, and correct it by hand against the packet and Chapter 7; find at least two. Submit the marked-up analysis with your corrections in place of the chatbot report and share link. If you take the compatibilist side in your dialogue, rebuild the printed claim that hard determinism is right at its strongest as a hard determinist would state it; if you take the hard determinist side, rebuild the printed claim about compatibilism at its strongest as a compatibilist would state it.

Part 7 — What to Submit

• The three completed tables from Part 4, including the count with its subtraction
• The four reconstructions, the same-shape argument for A3, and the four-to-six-line dialogue
• Written answers to all six analysis questions
• The chatbot critique report with its share link, or the equivalent route's marked-up flawed analysis

Deliverable:

A short Philosophy Workshop report on one illustrative harbor ferry packet: three completed tables (four arguments keyed for validity with reasons and the premise a defender of the other side rejects; the count of valid and invalid arguments with its subtraction; and the overnight ferry worked step by step), a same-shape argument for A3, a four-to-six-line dialogue between a hard determinist and a compatibilist ending in a plain sentence, written answers to six analysis questions, and a critique of a chatbot's version of the same work, or, on the equivalent route, a marked-up correction of the printed flawed analysis. Choose how you show it: written answers, a recorded explanation with a transcript, or labelled tables with short notes; 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.

Rubric

The rubric below shows how each submitted part is evaluated; bands are full, partial, or none.

Workshop evaluation criteria

Criterion	Full	Partial	None
Accurate reconstruction and validity judgment	All four arguments are in standard form, each form is named and keyed valid or invalid with a reason from the definition, each row names the premise a defender of the other side rejects, A3 has a working same-shape argument, and the count is worked with its subtraction.	Most arguments are reconstructed and keyed with reasons, but one is misnamed or miskeyed, a rejected premise or the same-shape argument is missing, or the count is missing or off.	The reconstructions are missing, or the keys rest on whether conclusions sound true rather than on form.
Thought-experiment test	The overnight-ferry table gives both answers for the overnight case, says with a reason whether the overnight change pulls the intuition differently from gradual repair, ties the question to numerical identity, and labels the case as a variation.	The table is mostly complete, but the comparison with gradual repair has no reason, or the sense of 'same' is not named.	No overnight-ferry table appears, or the variation is treated as Plutarch's own case.
Two positions stated fairly in dialogue	The dialogue gives the hard determinist and the compatibilist each their strongest point, has each answer the other, uses the fog crossing as a Frankfurt case tied to A2, and ends in one plain sentence naming where they disagree.	Both positions appear, but one is weakened (for example compatibilism presented as denying determinism), the speakers talk past each other, or the closing sentence is missing.	No dialogue, or only one side is stated.
Caught-and-corrected AI slip, on either route	The chatbot critique report, or the equivalent route's marked-up flawed analysis, quotes at least two errors, names the failure each shows, and corrects each by hand against the packet and Chapter 7; either route earns this band equally.	One error is quoted and corrected on either route, or errors are named without a correction.	No critique on either route, or chatbot output is pasted without checking it.
Accurate sourcing and reflection	The ship of Theseus is credited to Plutarch's Life of Theseus with any quoted line credited to Dryden's translation, the memory theory to Locke, Frankfurt's paper to 1969, both variations are labelled, nothing is invented, and the reflection answers option (a) or (b) with a reason.	The sourcing is accurate but the reflection is thin, or the reflection is strong but one attribution goes beyond the pinned record.	An invented quotation, work, or date appears, and there is no reflection.

Quality Gate

• Every argument is in standard form, with numbered premises and a conclusion line introduced by So.
• Every key says valid or invalid with a reason from the definition, the invalid argument has a working same-shape argument with true premises and a false conclusion, and no argument in the packet is called sound or unsound.
• The overnight ferry is labelled as a variation of Plutarch's ship of Theseus, the fog crossing as a variation on the shape of Frankfurt's cases, and the course's line about the planks is credited to Dryden's translation.
• Each position in the dialogue is stated as its strongest defenders would, and no verdict is announced on whether the ferry is the same ferry or whether the pilot was free.
• No quotation, work, date, or philosopher's view is invented anywhere in the submission.
• The critique quotes the chatbot or the flawed analysis and corrects at least two errors by hand.