# Thread: Philosophy problem dealing with logic...nice practice for computational logic

1. ## Philosophy problem dealing with logic...nice practice for computational logic

In my philosophy course the other day, my professor proposed a very interesting problem. Let me share it with you fellow AntiOnline gurus:

(I'll explain variables as I go)

A man named Theseus once sailed the seas in his ship dubbed the T.S. After many years of sailing, his ship fell into disrepair. He decided to take it to the nearest port city to have it restored. Once he arrived there, he docked his ship in Harbor A. Over a period of 1000 days, where A0 is the ship in Harbor A on Day 0 and A1000 is the ship in Harbor B on day 1000, a single wooden plank was removed each day, and replaced with a new one. Everytime this occured, however, the old plank removed from the ship in Harbor A was used to build a ship in Harbor B identical to the T.S. On Day 500, A500 is built with half new planks and half old, and B500 (the ship in Harbor B on day 500) is halfway finished, from the ground up, with the old planks removed from Ship A. On Day 1000, two completed ships are docked in Harbors A and B. The question is...which ship is the T.S.?

Think along the lines of characteristic identity and numerical identity...and how do you define when something begins and something ends.

Cheers,

2. Whichever one has the little metal plaque with the name and license info.

3. Neither one is, if every single part of the ship in harbor A was removed. if it still has some parts, then it is still the TS, but if not one single part of the original ship is remaining then it is no longer the TS.

The ship in harbor B is an exactly duplicate of the orignial TS using the original parts, but if the ship was in that bad of condition, it won't be sailing anywhere. If every part of the ship in harbor A was completely replased, then the ship in harbor A is a duplicate, but would be T.S. 2, but it could still bear the name TS as it is the only ship that sales with that name on it.

4. It all depends on your origional philosaphy, if western then neither (as #1 was rebuilt and none of the origional remain, #2 isn't a ship as it wont sail.) if eastern then #1 as even rebuilt its still the same ship.

5. A man named Theseus once sailed the seas in his ship dubbed the T.S. After many years of sailing, his ship fell into disrepair. He decided to take it to the nearest port city to have it restored. Once he arrived there, he docked his ship in Harbor A. Over a period of 1000 days, where A0 is the ship in Harbor A on Day 0 and A1000 is the ship in Harbor B on day 1000, a single wooden plank was removed each day, and replaced with a new one. Everytime this occured, however, the old plank removed from the ship in Harbor A was used to build a ship in Harbor B identical to the T.S. On Day 500, A500 is built with half new planks and half old, and B500 (the ship in Harbor B on day 500) is halfway finished, from the ground up, with the old planks removed from Ship A. On Day 1000, two completed ships are docked in Harbors A and B. The question is...which ship is the T.S.?

Think along the lines of characteristic identity and numerical identity...and how do you define when something begins and something ends.

harbor a = old TS
Harbor b = a1000

Both ships are the T.S. The ship in harbor b is made of the same planks from the original T.S. The ship in harbor a is the new T.S., which was completele rebuilt from the ground up. The ship in harbor a is the one Theseus will use to keep sailing, since the old one is a wreck. The ship in harbor b is the ship Theseus brought to get repaired. Identity dosen't define who the ship is, or isn't. Like your name. If I ask who you were, you would tell me what your name was. This is because we associate our identity with ourselves. However, this dosen't define WHO we are, which was what my question was. I'm still thinking about your second question.. I'll get back to you later on that one. Cheers.

6. This puzzle dates back to Heraclitus and his river-statements: the world is constantly changing, and Heraclitus wondered if someone could step into the same river twice. Heraclitus concluded (although there are different interpretations for his conclusion) that yes, one can step into the same river twice, even if the water you step into has changed.

The "solution" to the puzzle (although it is generally accepted amongst philosophers that there simply is no solution to this problem) depends on whether you accept the view that the identity of an object depends on the identity of the parts that compose the object, or not.

If you deny that view, then you'll be faced with problems as the one posted here. Deny that view, and there is no solution for your puzzle, simply because there will never be a "standard" agreement on where to draw the line ("Does a ship with one replaced bolt make a different ship? With two replaced bolts? Three? A different engine?")

If you agree with that view, then the "solution" is simple: none of the boats are the same, and the TS doesn"t exist anymore.

7. You question is full of assumptions. What really makes the T.S. the T.S. Is it that you can percieve it as so by interpreting the light waves which bounce off it with your eyes and brain? If that is the case, then the T.S. is only an image in your brain. Therefore, it is neither Ship A or B, it is merely the mental image you built of the T.S. when you decided to name it. Vague enough for ya?
-NeuTron

8. Here is some reading about Heraclitus

I agree with Heraclitus's philosophy about the material world. It is in constant change. He also says everything moves and nothing is at rest. Heraclitus concluded that you could NOT step into the same river twice.
The idea is this: since the composition of the river changes from one moment to the next, it is not the same river for any length of time at all. Everything is like a river in this respect. That is, nothing retains its identity for any time at all.
(taken from here )

Negative is right, if you accept this point of view, then neither ship is the T.S. However, according to the ancient Jewish way of thinking they both are the T.S. It just depends on which view you accept. If none, then Negative is right again. There is no solution because there isn't a standard agreement on where to draw the line. Which is what I think, there is no solution.

9. I believe I once heard of a man, doing a life sentence for murder,
who argued, after a number of years, that he should be released,
since he was no longer the same person who had comitted the
crime. After so many years, this is physically true. Every molecule
of your body has been replaced by fresh ones rebuilt from the food
you eat.

I think identity is more than just the parts, but more than the
name tag too.

10. Every molecule
of your body has been replaced by fresh ones rebuilt from the food
you eat.
I appologize for straying off-topic, but if that were true we would all have the key to mortality.

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