ar X iv : q ua nt - p h / 06 04 20 1 v 1 2 7 A pr 2 00 6 Partial Observers

We attempt to dissolve the measurement problem using an anthropic principle which allows us to invoke rational observers. We argue that the key feature of such observers is that they are rational (we need not care whether they are 'classical' or 'macroscopic' for example) and thus, since quantum theory can be expressed as a rational theory of probabilistic inference, the measurement problem is not a problem. The basic measurement problem in quantum theory is the fact that observers don't seem to be passive when it comes to the quantum domain. They seem to weirdly cause things to happen. This is obviously very difficult to come to terms with (and people have admirably tried to come to terms with it). We believe, however, that it is not something that we have to come to terms with and we shall outline in a moment why we don't. These measurement problems seem to arise when we introduce something that is not explained by quantum theory. For example, in the orthodox interpretation we introduce 'classical' observers, in decoherence theory we introduce 'macroscopic' objects, in other interpretations we invoke 'conscious' observers that cause wavefunctions to collapse or properties to actualise, and in the many worlds interpretation we say that the 'multiverse' splits into many 'universes' such that our experience is explained by the mere fact that we exist in a 'uni-verse' and not in the 'multiverse'. All these attempts to explain away the measurement problem invoke a significant amount of metaphysical baggage. In the following discussion we will also introduce something that is not necessarily explained by quantum theory, but that 'something' will have minimal spurious metaphysical baggage. We will assume something analogous to the anthropic principle; namely we claim that we exist and that we also try to be rational. This, it turns out, is all we need to dissolve the measurement problem. There is nothing in quantum theory that seems to contradict such a claim, and if it did contradict such a claim (rather than remain mute about it) we would probably reject quantum theory. Thus we argue that there is nothing to stop us from making this quasi-anthropic assumption.