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2.4 Irrelevances to the debate

2.4.3 Ability to modify hardware

The ability of an organism to modify its own "hardware", for example when a protein acts on its own DNA (e.g. to repair it), or at least acts to effect the interpretation of that DNA into proteins, is sometimes compared to a Turing machine which cannot directly effect its "hardware" (as usually defined).

This separation of hardware and software is arbitrary unless "physicality" can be shown to be important attribute, effecting what can be computed. Otherwise, there is nothing to stop a Turing machine simulating such a change in hardware (including its own). For example, imagine a Turing machine which could execute an instruction-type that could change one of its own instructions. It would seem at first glance that this new machine "goes beyond" the usual version, but this is not so. A normal Turing machine can compute exactly the same functions as the new enhanced machine, because although it cannot change its own instructions, those simple instructions can be combined in a sophisticated way to simulate the computation of the enhanced machine.

Several such "essential" characteristics of such physicality are possible.

  1. The presence of noise in analogue systems (for this see Section 2.4.4 below).

  2. A fundamental difference between matter and symbols (as in [10]). This is closely connected with the problem of measurement.

  3. That arbitrarily small changes in the initial conditions have significant effects on the outcomes. The significance of this is either that noise (for this see Section 2.4.4) can then be significant or that due to its analogue nature you can never know the initial conditions sufficiently (for this see Section 2.4.2 above).

We are thus left with the argument as to a fundamental dichotomy between matter and symbols. Whether or not this turns out to be a fundamental distinction, it is not clear why this would effect of the ability to modify one's own hardware (or simulate such a modification in software).

Pragmatic Holism - Bruce Edmonds - 22 FEB 96
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