Observation has been a fundamental resource for the philosophical understanding of scientific theories since the early days of 20th Century philosophy of science. What constitutes a direct observation of something, which knowledge we can gather about the natural world that is understood and explained by theories are central epistemological questions that have been addressed in a variety of ways. In this thesis I have developed a previous interest in the problematic of the observability of the fundamental constituents of reality by deepening my study within one of our most successful theories about matter, namely, quantum mechanics. The latter constitutes an interesting field to study observation on independent grounds, as the way in which quantum objects behave upon certain types of interaction displays properties that are unique in their own right.
The richness of such a starting point has demanded a clear research plan in order to achieve a compromise of generality and precision which makes this work bath interesting to a broad extent in the philosophy of science, but also sharp, by carrying out the analysis of a well-defined topic in the philosophy of physics. For this reason I have opted to consider one case study - Bell's theorem, and to produce a subsequent philosophical analysis based on the latter. Bell's theorem is a fundamental result in the foundations of quantum mechanics, which uncovers in an uncontroversial manner one aspect of the essential uniqueness of quantum entanglement. By deriving a constraint for physical correlations from classical assumptions independent of quantum theory, it achieves to show that the correlations yielded by entangled systems are stronger than those that characterize classical systems. On a theoretical level, this result has an overarching character that has provided unique insights into quantum phenomena, but that can also be applied to other theories. Its attractiveness for my research however is largely due to the extended empirical confirmation of the quantum predictions, which have corroborated the result, and which represent a rich resource of examples of observation in the quantum domain. In order to understand the experiments and their epistemological value, I have delved into the formal, theoretical aspects of the theorem in depth, before passing to a careful study of the goals the experiments had to achieve and how they have met such targets. After having completed the analysis of the case study, I have proceeded to consider the latter from a philosophical perspective, exploring connections with relevant debates in the philosophy of science such as the theory-ladenness of observation, scientific realism, underdetermination, and the types of assumptions supporting the choice of a particular scientific theory over a competitor.
The results of the thesis can be summarized in three points. First, the peculiar problems related to observation within the quantum domain do not derive from the limits of our current understanding of the observation processes. The crux of the matter lies rather in the very mathematical apparatus of quantum mechanics used to represent physical systems, which systematically leads to contradictions with the way in which the latter are measured and experienced. Second, I argue - at a preliminary stage - that the correct manner to understand quantum mechanics is not in terms of a theory that directly models an ontology, but rather as a categorical toolbox that provides us with the means to think of the world as quantum. Third, the current supporters of some quantum theories or interpretations of quantum mechanics ground their arguments for the superiority of their chosen view over others on roots of normative character, i.e., on what science ought to do, which they use as an argumentative basis for the preferability of their quantum theory or interpretation of quantum mechanics.