This paper compares the free energy neuroscience now advocated by Karl Friston and his colleagues with that hypothesised by Freud, arguing that Freud's notions of conflict and trauma can be understood in terms of computational complexity. It relates Hobson and Friston's work on dreaming and the reduction of complexity to contemporary accounts of dreaming and the consolidation of memory, and advances the hypothesis that mental disorder can be understood in terms of computational complexity and the mechanisms, including synaptic pruning, that (...) have evolved to reduce it. (shrink)