Conclusions

This weakness represents also the strength of our point of view, which allows us to highlight the possibility that an entity could exist without possessing intrin­sic properties.

For the orthodox interpretation, which completely denies the physical reality of the wave function, this relational character would be peculiar to atomic particles. To a certain extent this is true, given that in an experiment of complementary type, such as that considered above, what we reveal depends on our experimental arrangement. However, the very act of detection is by definition the detection of a particle or the recording of an event (and this result can also be stored and commu­nicated), and this explains the asymmetry between ontological recordable events and relational wave-like entities, the assumption that Agazzi, as we saw in Sect. 3, considered as the truly new element in the conception of the quantum wave.

Another strong reason to ascribe physical reality to quantum waves is that between wave-like and particle-wave behavior, there is a continuum of possible cases, as it has been shown by the existence of the so called smooth complemen­tarity, i.e. the possibility of a smooth variation between wave-like and particle-like behaviour and consequently of infinite intermediate possibilities between the two extreme alternatives (Mittelstaedt et al. 1987). Obviously, this runs against Bohr’s idea that complementarity is a sharp relation in which we have either the wave or the particle.

Our proposed experiment seems to show that perhaps one could distinguish experimentally between EPR’s realism of properties and the realism of theoreti­cal entities: the presence of correlations between remote detections of photons would highlight the physical reality of the quantum wave, violating the realism of EPR and confirming the predictions of quantum mechanics, as happened with the experimental controls of Bell’s theorem, while the absence of correlations would disprove quantum mechanics in favor of EPR’s empirical realism.

The former result, which is certainly the more probable (although we cannot rule out the second one without before running our experiment) would be a direct experimental confirmation of Agazzi’s realism of entities, and of the need to find a counterpart in physical reality for fundamental theoretical concepts.

A new feature of our experiment is also that it does no longer discriminate between a realistic and an antirealistic (Copenhagen like) interpretation, but between two different realistic interpretations of quantum mechanics. In my opin­ion this represents a decisive confirmation of the necessity of a realist interpreta­tion of scientific theories, which Agazzi has always considered an epistemological assumption indispensable to any serious philosophical inquiry.