I ran across this idea a while back on one of the science blogs I follow, but had just glanced over and forgotten about it until someone asked about it on LinkedIn yesterday.

Nick Bostrom of Oxford University asked “Are You Living In a Computer Simulation?” in a 2003 paper. From the abstract: “This paper argues that at least one of the following propositions is true: (1) the human species is very likely to go extinct before reaching a “posthuman” stage; (2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); (3) we are almost certainly living in a computer simulation.”

Because it has continued to be a popular / controversial topic, Bostrom has set up a web site Are You Living in a Computer Simulation? where “[...] you can peruse the debate that followed the paper presenting the Simulation argument. The original paper is here, as are popular synopses, scholarly papers commenting on the first paper, and a couple of replies to these comments.”

Note that the paper itself isn’t an argument for or against #3 (we are a living in a simulation); rather that at least one of the three propositions is true. The interesting (and perhaps creepy to some) point is that if you assume some future post-human civilization can simulate their “ancestors” (us), and that they do so at all, then vastly more simulated humans will have existed than ever physical humans did. Thus any person at random who ponders this question is much more likely (p ~ 1.0) to be a simulation than an original physical human.

So, how can you tell? Well, you probably can’t, unless the entity running the simulation wants you to. If by some means you did discover (or came close to discovering) you’re a simulation … you get restored from backups … or deleted … or the whole simulation would get reset. Ouch.

At least read the NY Times article “Our Lives, Controlled From Some Guy’s Couch” (linked to from the site above) for a lighter take on the idea.

Oh, and the obligatory Wikipedia link: Simulated Reality.

That in turn reminds me of a long-ago (80′s ?) discussion with a friend about whether gradual replacement of all “components” over time would leave someone the “same” person, and would that be qualitatively different that a sudden replacement of everything at once. In essence, I suppose, it came down to whether there was continuity of sense-of-self.

The truth is that it’s happening to us daily, without need of any silicon substrate for our consciousness; or plastic, metal, and ceramic parts to replace lopped off limbs or damaged organs. According to “Body Story”, a Discovery documentary I happen to be watching (one more disc to go), almost no part of anyone’s body is over 10 years old; some parts are renewed after only a few days.

In any case, like many philosophical quandries this actually has a name and a long history. Wikipedia says, “The Ship of Theseus paradox, also known as Theseus’s paradox, is a paradox that raises the question of whether an object which has had all its component parts replaced remains fundamentally the same object.” Quoting from Plutarch’s “Theseus”:

The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.

Elsewhere he quotes Heraclitus:

“It is impossible to go into the same river twice”, said Heraclitus; no more can you grasp mortal being twice, so as to hold it. So sharp and so swift its change; it scatters and brings together again, nay not again, no nor afterwards; even while it is being formed it fails, it approaches, and it its gone.

The whole XVIII paragraph eerily parallels the “Body Story” segment on aging.

The Wikipedia article also mentions more recent variations of the paradox — such as George Washingon’s axe, John Lock’s socks, Jeannot’s knife, and contemporary references to it in fiction and media. I could not help but form the mental image the ship of Theseus, made of wood hewn by Washington’s axe, floating on Heraclitus’s river, me aboard and wearing Lock’s socks, mended with Jeannot’s knife. (Sorry, sorry).

It occurs to me that programmers must also decide what it means to be the “same” thing. For example, in Java you must be careful in choosing == vs .equals(); in Lisp, you must pick =, EQ, EQL, EQUAL, or EQUALP.

Perhaps, as said in Ecclesiastes, “That which has been is that which shall be; and that which has been done is that which shall be done: and there is no new thing under the sun.”

Bad scientist! No poems for you, gnomekiller!

Well, that’s how it feels, if you get emotionally attached to the gnomes, and then a scientist says there aren’t any gnomes. It takes a strong mind, a deep honesty, and a deliberate effort to say, at this point, “That which can be destroyed by the truth should be,” and “The scientist hasn’t taken the gnomes away, only taken my delusion away,” and “I never held just title to my belief in gnomes in the first place; I have not been deprived of anything I rightfully owned,” and “If there are gnomes, I desire to believe there are gnomes; if there are no gnomes, I desire to believe there are no gnomes; let me not become attached to beliefs I may not want,” and all the other things that rationalists are supposed to say on such occasions.

But with the rainbow it is not even necessary to go that far. The rainbow is still there!

All this just to say it reminded me of something I scribbled back in 1977: By Way Of Reflection.