The original Simulation Argument doesn’t require a simulation at the atomic level:
The argument we shall present does not, however, depend on any very strong version of functionalism or computationalism. For example, we need not assume that the thesis of substrate-independence is necessarily true (either analytically or metaphysically) – just that, in fact, a computer running a suitable program would be conscious. Moreover, we need not assume that in order to create a mind on a computer it would be sufficient to program it in such a way that it behaves like a human in all situations, including passing the Turing test etc. We need only the weaker assumption that it would suffice for the generation of subjective experiences that the computational processes of a human brain are structurally replicated in suitably fine-grained detail, such as on the level of individual synapses. This attenuated version of substrate-independence is quite widely accepted.
Neurotransmitters, nerve growth factors, and other chemicals that are smaller than a synapse clearly play a role in human cognition and learning. The substrate-independence thesis is not that the effects of these chemicals are small or irrelevant, but rather that they affect subjective experience only via their direct or indirect influence on computational activities. For example, if there can be no difference in subjective experience without there also being a difference in synaptic discharges, then the requisite detail of simulation is at the synaptic level (or higher).
But more crucially:
Simulating the entire universe down to the quantum level is obviously infeasible, unless radically new physics is discovered. But in order to get a realistic simulation of human experience, much less is needed – only whatever is required to ensure that the simulated humans, interacting in normal human ways with their simulated environment, don’t notice any irregularities.
As I’ve said in previous comments I’m inclined to think that simulations need that amount of detail to accurately use them to predict the future. In that case maybe that means that I had in mind a different version of the argument, whereas the original Simulation argument does not asume that the capacity to accurately predict the future of certain systems is an important incentive for simulations to be created.
About the quantum part… Indeed it may be impossible to determine the state of the system if it entails quantum randomness. As I wrote :
“let’s note that we did not take quantum randomness into account [...]. However, we may be justified not taking this into account, as systems with such great complexity and interactions make these effects negligeable due to quantum decoherence” .
I am quite unsure about that part though.
However I’m not sure I understood well the second quote. In “Simulating the entire universe down to the quantum level is obviously infeasible”, i’m not sure if he talks about what I just wrote or if it is about physical/technological limitations to achieve so much computing power and such detail.
I think Bostrom is aware of your point that you can’t fully simulate the universe and addresses this concern by looking only at observable slices. Clearly, it is possible to solve some quantum equations—physicists do that all the time. It should be possible to simulate those fee observed or observable quantum effects.
The original Simulation Argument doesn’t require a simulation at the atomic level:
But more crucially:
As I’ve said in previous comments I’m inclined to think that simulations need that amount of detail to accurately use them to predict the future. In that case maybe that means that I had in mind a different version of the argument, whereas the original Simulation argument does not asume that the capacity to accurately predict the future of certain systems is an important incentive for simulations to be created.
About the quantum part… Indeed it may be impossible to determine the state of the system if it entails quantum randomness. As I wrote :
“let’s note that we did not take quantum randomness into account [...]. However, we may be justified not taking this into account, as systems with such great complexity and interactions make these effects negligeable due to quantum decoherence” .
I am quite unsure about that part though.
However I’m not sure I understood well the second quote. In “Simulating the entire universe down to the quantum level is obviously infeasible”, i’m not sure if he talks about what I just wrote or if it is about physical/technological limitations to achieve so much computing power and such detail.
I think Bostrom is aware of your point that you can’t fully simulate the universe and addresses this concern by looking only at observable slices. Clearly, it is possible to solve some quantum equations—physicists do that all the time. It should be possible to simulate those fee observed or observable quantum effects.