The theory of functionalism holds that mental states are constituted solely by the functional organisation of an implementing system. We propose that the specific mechanism supporting both intelligence and consciousness is data compression. Recent approaches to cognition and artificial intelligence, based on a branch of theoretical computer science known as algorithmic information theory (AIT), have proposed a computational view of induction, prediction, understanding and consciousness which is founded on this concept. Building on existing literature we propose the term ‘compressionism’ as a label to unite theories which recognise intelligent, cognisant systems as sophisticated data compressors. We show how data compression can shed light on information binding and offer a novel perspective on the hard problem of consciousness.