PhD defence S.K.J. (Sven) Aerts

Dissertation in short:

Observation is the bridge between reality and our representations of reality, between experiment and theory, between the physical phenomenal world and the cognitive inner world. The role of observation is so important that it would be desirable to have a theoretical description of the physical observer, but precisely because observation is key in testing a theory, the snake bites its own tail. After all, a perfect theoretical description of the observer would either be wrong or make that same observer superfluous. This problem is particularly present in the case of self-observation because the division between what is observed and who is observing disappears. We show by means of aso-called diagonal argument that an observer is not able to observe all its own properties. We will also argue that this can be seen as a primitive precursor of the infamous measurement problem in quantum mechanics. 

Uncertainties about self-observation will induce uncertainties about other types of observation too. We usually mitigate the effect of this uncertainty by collecting data through repeated measurement. However, in the light of the foregoing, we can and should not rule out the possibility that we are not only averaging over an ensemble of systems, but also over an ensemble of observers. We show that a model that incorporates both types of ensembles can reproduce the probabilistic machinery of quantum mechanics.