Re: Subjective counterfactuals

Nick Bostrom (
Mon, 5 Apr 1999 02:21:30 +0000

Hal wrote:

> Simply put, it is meaningless to ask whether a replay is conscious; it
> is meaningless even to ask whether a second run of a conscious program
> further instantiates the consciousness. There is no subjective fact of
> the matter to resolve, and so there is no objective problem which can
> be solved, either.

I see a couple of problems with this view (I'm not saying it is wrong). First, ethically: does it matter if one instantiates a suffering-state more times than necessary? Second, epistemologically, given observer self-selection (i.e. that you should consider yourself as if you were a randomly selected observer) then it makes a difference whether multiply instanciated programs should be counted more than once. Also consider the slightly weird effect that two very slightly distinct programs give rise to two subjects of experience, but remove the slight discrepancy, and voila, there is no fact of the matter any longer as to whether there is one or two of them. (It's not hard to think of an example that combines this with the epistemological concern.)

Nick Bostrom Department of Philosophy, Logic and Scientific Method London School of Economics