It is with great pleasure that I have the opportunity to introduce this special issue on the integrated information theory (IIT) of conscious-ness for the Journal of Consciousness Studies. IIT is the view that consciousness is integrated information in a system, the degree of which is quantified by a function denoted by the Greek letter Φ. IIT is developed by its originator Giulio Tononi and his colleagues at the Wisconsin Institute for Sleep and Consciousness (WISC) and aims to explain how phenomenal experience comes about in certain physical systems.
In recent years IIT has been gaining more and more attention. Pre-sumably, this is due not only to the scope of the claims IIT makes but also the boldness of the theory itself. IIT offers what proponents claim is a toolbox for scientifically and mathematically measuring phenom¬enal experience. Many would feel that such an endeavour is a Herculean feat to accomplish or otherwise near impossible given our modern tools. Nonetheless, those developing IIT and its proponents think IIT is on the right track for providing such an explanatory framework.
I think the attention IIT has garnered derives principally from the conjunction of two theses to which IIT seems committed: that being (1) phenomenal experience is real and thus requires explanation, this is in contrast to those positions that call into doubt the veridicality of such properties of experience and think they should be eliminated given a sufficient theoretical framework or that they are merely illusory; and furthermore (2) it provides a mathematically precise and scientific means to test hypotheses concerning phenomenal experience understood as integrated information.
The modern position those interested in researching consciousness often find themselves in is that there is no natural place for phenomenal experience in our current understanding of nature, which thus motivates physicalists and anti-physicalists to think, for obviously very different reasons, that consciousness has no straight-forward place in nature. I think the conjunction of these two facets of IIT, allowing one to both be a realist about phenomenal experience and offering a scientific framework to investigate the phenomenon, makes IIT appealing for a number of people. The interest in IIT comes in many forms, as the contributions within this special issue will surely reflect.
It’s unsurprising that a theory like IIT is met with rather intense scrutiny given the scope of explanation which its founder, Giulio Tononi, thinks the theory provides, that being both the level and con-tent of experience. Given that integrated information is meant to be a kind of fundamental measure, the target of the theory is not only the human nervous system, but any physical system which has integrated information. With such a breadth the theory naturally opens itself up to a number of philosophical worries and questions. This broad scope of IIT is concurrently one of its greatest assets and detriments, as it simultaneously makes the theory intriguing and compelling but also opens the theory up to a number of objections.
The contributions for this special issue in their own way reflect the scope of IIT, in that each approaches IIT from a different perspective and from a number of disciplines, though all are philosophical in their own right. My intent with this special issue was to present something of a mosaic of different work on IIT, not so much a targeted issue on some question concerning IIT or essays aimed at a target article, but rather a venue for those interested in the theory to present their work on topics concerning IIT. My hope was to show that IIT’s scope is not only reflected in the theory itself, but also in those who engage with the theory in philosophical and scientific communities. By doing so, my intention was to open up different areas of discussion surrounding IIT and to further increase engagement with the theory.
To some extent all the contributions are asking interpretive questions about IIT. Three separate contributions focus specifically on the interpretation issue for IIT, those being Adam Pautz’s, Kelvin McQueen’s, and Carlos Montemayor et al.’s. Adam Pautz focuses on how one is meant to understand talk of ‘amount/degree/level of Φ’ in IIT. Pautz outlines a number of possible interpretations for what those developing IIT might mean by ‘amount/degree/level of Φ’. He also argues that standard neuroscientific explanations about the quality of experience seem to offer a better explanation about the quality of experience than the view offered by IIT. Kelvin McQueen’s contribu-tion asks whether we might undertake a similar interpretive project which quantum mechanics underwent in order to separate it from the problematic philosophical positions of its founder, Niels Bohr. McQueen looks to outline what he calls an ‘interpretation-neutral IIT’, one that is freed from as many metaphysical and epistemological assumptions as possible. Finally, Carlos Montemayor, J. Acacio de Barros & Leonardo P.G. De Assis’s essay concerns issues of scientific modelling and methodology — specifically they argue that any theory of information needs to adhere to three constraints which they outline in their contribution: implementation, formalization, and representa¬tion. Although they think there are issues currently in how IIT might satisfy these constraints, they end on a positive note, claiming IIT’s enormous potential in meeting these worries head on.
Three contributions take a different interpretive stance and investi-gate the relationship of IIT with various metaphysical positions. Matthew Owen’s contribution investigates the similarities between IIT and Aristotle’s hylomorphism, focusing on the Thomistic variant. Given IIT’s apparent adherence to something akin to a causal powers ontology, Owen proposes that IIT, as well as hylomorphists, might benefit from a discussion on these matters of shared contact. Hedda Hassel Mørch’s contribution sets up what she calls the intrinsicality problem for IIT: if consciousness is intrinsic then how can it be identical to maximal Φ when Φ is an extrinsic measure? Mørch argues that this problem isn’t unique to IIT, but applies to any theory of con-sciousness, and motivates this by setting up a trilemma of three theses: intrinsicality, non-overlap, and reductionism. She explores whether IIT needs to reject intrinsicality or if the theory would be better off rejecting either reductionism or non-overlap. Matteo Grasso’s essay focuses on comparing IIT with another metaphysical framework to explain consciousness that has been gaining popularity over the years, Russellian monism. He notes that IIT is often compared to pan¬psychism and/or Russellian monism, and looks to explore this com¬parison more closely, specifically looking at categoricalist versions of Russellian monism. Ultimately, Grasso argues that IIT’s core notion of intrinsic cause–effect power makes it incompatible with categori¬calist versions of Russellian monism and suggests that IIT is in a better position than Russellian monism to tackle fickle qualia argu¬ments, which he argues shows IIT is better equipped to explain the content of experience than categoricalist Russellian monism.
The last two contributions focus on matters intimately related to the formal aspects of IIT. In Adam Barrett and Pedro Mediano’s contribu¬tion they question whether Φ is well-defined for general physical systems. Given that Giulio Tononi and those that defend IIT have claimed that Φ is a fundamental observer-independent property, they argue that, unless Φ is well-defined for general physical systems, IIT fails to secure such a claim regarding Φ. Luis Favela’s contribution explores the connection between IIT and complexity science, arguing that IIT would benefit from finding a natural home within the broader framework of complexity sciences. Favela points out the similarities, as well as the dissimilarities, between IIT and complexity sciences.
I would like to end by thanking all of the authors for contributing to this special issue and for all the work they put into their respective contributions. I would also like to thank the reviewers who volun-teered not only their time but their expertise — they have helped to make the issue even better and for that they have my sincerest thanks. Thank you to the managing editor of JCS, Graham Horswell, for inviting me to edit this special issue and for his help in navigating the task of being guest editor — his help and advice were invaluable. I would also like to extend my gratitude to Giulio Tononi and his colleagues at the Wisconsin Institute for Sleep and Consciousness, whose lab I visited during the autumn of 2018 and where I completed the editing of the special issue during my stay. Giulio and all those working at WISC were generous with their time, kindness, and expertise and it is an intellectual debt I doubt I’ll ever be able to pay back.