RE: Computability of consciousness
Thu, 1 Apr 1999 13:21:21 -0800

Nick Bostrom, <>, writes:
> I think this is the idea behind David Chalmer's recent definition of
> what it means for something to be an implementation of a program (or
> computation). The causal structure of the implementation has to match
> the structure of the program. I don't have his book handy at the
> moment however.

I should read Chalmers' book. I've been hoping to cheat and get it from the library, but it's on the reserved book list for some course.

> Another example we may consider: Suppose we have a computer running
> an upload for 10 seconds. Suppose we computer has discrete time. Then
> we could in principle construct one computer (or one RAM chip) for
> each time step of the simulation; and we could load each of these RAM
> with the data that the RAM in the original computer had at the
> corresponding time. We can place all these RAM chips in one long row.
> In some sense, we then have what looks like the same structure
> instanciated in two places in spacetime -- once as a spatiotemporal
> process, and once as a spatial pattern. We presumably want to say
> that only the former gives rise to a consciousness. And the relevant
> difference seems to be that in the case of the process, the various
> states are causally connected, whereas with the spatial pattern that
> is not so.

In Greg Egan's novel Diaspora there is a race which apparently does choose to live via spatial sequencing similar to what you describe. They build a different instance of the computer they live in for each time step of the simulation. Each instance is a solid block and has no ability to change state. Luckily they have parallel dimensions or something to work with, so that it doesn't really take up that much room. You'd think it would be slow, but apparently they don't care.

Egan seems to invite us to consider this spatial sequencing to be as effective as temporal sequencing in terms of creating consciousness.

Of course, the spatial sequencing is by its nature temporal as well, since they can't build the nth computer until they've finished with the n-1th one. This might give an "out" for those who want to see consciousness as intrinsically having a temporal dimension. They might say that there was a "wavefront" of consciousness whose "now" was the moment of the construction of each new block of matter. The fact that the old blocks of matter are left behind is, um, immaterial (yuk, yuk).