Saturday, September 12, 2009

Prestigious Programmers Process Persons Philosophically

Like the “mind/body problem” discussed earlier, I think Programmers have interesting input for Philosophers on another perennial topic of theirs: “personal identity” and the side topics of teleportation and duplicating people (“persons” in philosophy speak). In addition to a perspective on whether the transported person is the same as the original (which is the normal focus of attention), programmers also have an insight into an oft overlooked aspect: Why would a duplicate ever act differently than the original?

Beam Me Up, Scotty

In [Western] Philosophy, “personal identity” is the thing that links a past, present, and future “you” such that it is right to hold “present you” accountable for the acts of “past you”, and “present you” cares about what happens to “future you”. In many philosophical discussions of “what is a person”, and “what is consciousness”, the topic of teleportation (aka teletransportation) comes up. To the non-philosopher, it is probably surprising that science fiction is discussed in scholarly debates about what is “really real”. The Star Trek transporter (and many variations of it) are discussed because it stops participants from getting away with shallow “common sense” answers. It presents problems with simplistically defining a person as the collection of atoms that embody that person, or as an unbroken series of memories, or as a soul (of the Judeo-Christian type).
For example:

  • When you re-materialize from transporting, if you are made up of different atoms than constituted you before you left, are you really you? Or, are you a clone with the original you having died?
  • When you re-materialize, are you still you because you are made up of the same unbroken series of memories? But, if you say yes, what happens if the transporter fails to destroy the original? If the one now on Mars is you then who is the person still standing on the transporter pad here on Earth?
  • If you consider teleportation as constituting a “break” in memory/consciousness, and therefore you would not be the same person, then why are you considered to be the same person after being unconscious with no memories for 8 hours each night?
  • If you have/are a soul then what happens to it? Does the re-materialized you get it? What if the original you wasn’t destroyed?
Artie Deco and 4-Q-2

A variant on transporter discussions is simply around duplicating a person, and it is here that I would acquaint philosophers with the Unix system call: fork().

In the Unix operating system, there are “processes” that run (apparently) simultaneously, and are analogous to persons. Like a person, each process has its own memories, its own intentions, and its own “location in space-time”. And, via the fork system call, processes can be duplicated. In fact, the fork scenario is even stranger than a transporter…

Imagine a special small room, and inside is a black vending machine with a single button. If you enter the room and push the button, a cell phone is dispensed. Except that when you pushed that button, a copy of you was created in another dimension, and to both you and the copy, it seems like nothing has happened. It appears to each that they are the one who just pressed the button and was given a phone. When each copy leaves the room, they are back in the same original dimension, and each may encounter and interact with the other.
Now, how would you know if you are the original or the copy? Does “original” and “copy” even have meaning here? Most people would try to answer in terms of “who has the original atoms” and the like, and if one copy did have them then the situation is the same as the broken transporter scenario. So, imagine further that until either copy does something to cause its body to diverge from the other, the copies even share the same atoms. On an atom by atom basis, each copy only gets its own as either copy does something to diverge on that particular atom. And, it is effectively random which copy keeps any particular atom as they diverge over time. SO, which one is the original, and which one is the duplicate? I.E. which one is the “same” person as the one that originally hit the button?

As contrived as that scenario sounds, that’s what happens when Unix forks a process (with the help of copy-on-write virtual memory). And programmers have an answer as to which one is the “same” as the original. …drum roll please… ahem…

“It is so arbitrary that God has to tell each whether they are the original or the copy!”

What do you think the cell phone is for? Actually, the cell phone serves two purposes (to keep the analogy really strict); each phone has a text message with either the phone number of the copy (meaning that YOU are the original), or a zero, meaning that you are the copy. The original is free to call the copy.

But I Don’t Want To Be The Copy

Here is the part that Star Trek, et al, usually gets wrong, and Philosophers don’t seem to ponder: Why do the copies act differently than each other? One mitigating factor is that each copy is usually materializing in a different location, or a different time, or with special defects (like milquetoast Capt. Kirk versus Mr. Hyde Capt. Kirk), so they can be forgiven for not having each copy act in lock step. But in the fork scenario, they exist in the same situation, and therefore would do exactly the same thing as each other. Whoa! What about Free Will and all that stuff? Well, given the same location, environment, memories, “programming” if you will, why shouldn’t they do exactly the same thing as each other?

With Unix processes, unless the programming takes note of whether it is the original or not, and unless it does different things based on that information, each copy will attempt to do the same things. They will only diverge as they both attempt to do something that only one will be allowed to do. For example, locking a file, or reading the very next bit of data from an already open file. The Unix operating system (aka God), will arbitrarily pick one of the copies to succeed when both try simultaneously. [Think multiple CPUs all you geeks shouting that they don’t really do things simultaneously.] So, the copies begin to fitfully diverge as one succeeds then does what it planned to do upon success, and the other one fails then does what it was planned to do upon failure.

Now, programmers know that to be productive, they must decide what they want each copy to do, and write the program in such a way that each does what it is supposed to. With people, you must know what will happen when you press that vending button, and why you are pressing it, and what you want each copy to do, AND HAVE THE WILLPOWER TO DO IT!

It does no good to have a plan about what the “copy” is supposed to do if you have the personality that is going to decide after it’s too late that you don’t want to be the copy! If your "programming" is such that, after pressing the button, you decide to not look at the text message because now you don't really want to know...well then the OTHER copy is going to do the exact same thing! [If you do look but decide to ignore it then, unlike a program, it gets to be a psychological issue of whether you really can ignore it.]

There is a wonderful exploration of all these aspects in the movie “The Prestige”. I would point out each scenario, but I so want you to see it if you haven’t already, and I don’t want to spoil all the twists and turns at the end.


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