Vol.:(0123456789) Foundations of Science https://doi.org/10.1007/s10699-020-09696-8 1 3 Zeilinger on Information and Reality Ali Barzegar 1  · Mostafa Taqavi 1  · Afshin Shafee 2 © Springer Nature B.V. 2020 Abstract According to Zeilinger’s information interpretation of quantum mechanics ‘the distinction between reality and our knowledge of reality, between reality and information, cannot be made. They are in a deep sense indistinguishable’. This is what we call Zeilinger’s thesis. This thesis has been criticized as a lapse into ‘informational immaterialism’ and amounting to nothing more than a tautology. However, we will argue that this criticism is based on a pre-Kantian view of reality, namely metaphysical realism which could be questioned on the basis of Putnam’s arguments. Furthermore, it will be argued that to understand Zeilinger’s thesis one should abandon the pre-Kantian perspective of metaphysical realism and adopt a post-Kantian perspective on the relationship between the mind and the world. Keywords Zeilinger · Metaphysical realism · Putnam’s internal realism · Information · Quantum mechanics · Kant 1 Introduction In the last decades, we have been witnessing a turn towards epistemic interpretations of quantum mechanics. Notable epistemic interpretations include Fuchs (2002, 2010), Zeilinger (1999, 2010), Healey (2012, 2017), Friederich (2015), and Boge (2018). Accord- ing to all these interpretations the quantum state somehow represents the knowledge, infor- mation or beliefs of the user of quantum mechanics. However, Zeilinger’s information interpretation of quantum mechanics with its peculiar notion of the relationship between information and reality has proved a controversial epistemic interpretation of quantum mechanics. Zeilinger famously comments on the fundamental role of information in the context of quantum mechanics in the following way: So, what is the message of the quantum? I suggest we look at the situation from a new angle. We have learned in the history of physics that it is important not to make distinctions that have no basis—such as the pre-newtonian distinction between the * Mostafa Taqavi m_taqavi@sharif.edu 1 Philosophy of Science Department, Sharif University of Technology, P.O. Box 145888-9694, Tehran, Iran 2 Research Group on Foundations of Quantum Theory and Information, Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran