Consciousness and complexity: Neurobiological naturalism and integrated information theory

•We discuss and compare two prominent neuroscientific theories of consciousness: Integrated Information Theory and Neurobiological Naturalism.•We compare them from an ontological perspective, asking three questions: What is the nature of consciousness according to the theory? In what way does consciousness exist according to the theory? What is the relation between experience and its substrate within the theory?•We compare them from an epistemological perspective, asking two questions: How does the theory distinguish between conscious and nonconscious systems? How does the theory explain the character of consciousness in a system?•We conclude that, while both IIT and NN present ambitious goals, a potential unification seems unaccomplishable at the moment due to the radical differences in framework assumptions.