Could a sufficiently detailed computer simulation of consciousness replicate consciousness? In other words, is performing the right computations sufficient for artificial consciousness? Or will there remain a difference between simulating and being a conscious system, because the right computations must be implemented in the right way? From the perspective of Karl Friston's free energy principle, self-organising systems (such as living organisms) share a set of properties that could be realised in artificial systems, but are not instantiated by computers with a classical (von Neumann) architecture. I argue that at least one of these properties, viz. a certain kind of causal flow, can be used to draw a distinction between systems t...