In this paper,we outline a recent theory of positive symptoms of schizophrenia,such as hallucination and delusions of passivity experiences. We first introduce a vision theory based on Bayesian estimation and our computational theory of visual cortical areas. These suggest implementations of Helmholtz’s theory of unconscious inference in the brain. Next, we show the mechanisms for predicting consequences of motor actions,which is important for sense of self-agency and self-monitoring. Finally,we discuss the conceptual framework explaining positive symptoms in schizophrenia based on recent brain imaging studies.