One in a series of talks from the 2019 Models of Consciousness conference. Adam Barrett Sackler Centre for Consciousness Science, University of Sussex, UK Integrated Information Theory (IIT) has gained a lot of attention for potentially explaining, fundamentally, what is the physical substrate of consciousness. The foundational concepts behind IIT were extremely innovative, and it has been very exciting to see certain predictions being upheld in experiments. However, many problems have been uncovered with the mathematical formulae that IIT proposes for measuring consciousness exactly. This has led to fragmentation amongst consciousness researchers, between those who accept IIT, and those who reject IIT. In this talk, I make the case for a `weak’ form of IIT as a pillar of a future theory of consciousness, and summarise some of the problems with `strong’ IIT. Weak IIT maintains that neural correlates of consciousness must reflect two key aspects of phenomenology. First, that each conscious moment is extremely informative (it is one of a vast repertoire of possible experiences). Second, that each conscious experience is integrated (it is experienced as a coherent whole). I review some of the empirical evidence for this, in the form of greater diversity and connectivity in observed neural dynamics from conscious versus unconscious humans. I then discuss how the Phi measure of integrated information is not well-defined, and not unique given the axioms of IIT, and hence that the current version of strong IIT should be rejected. I conclude with some discussion on possible ways forward. Filmed at the Models of Consciousness conference, University of Oxford, September 2019. Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/