It is constitutive for Maturana that at the moment of experiencing we cannot tell a perception from an hallucination. From his analysis, the science of neurophysiology has failed to generate a mechanism which could explain our hearing/seeing objects external to us, independent of us. Maturana asks "How come we make mistakes in perception if it is the case that we directly see an objective reality?. He points out that at the moment of perceiving we never know that we are making a mistake - this awareness of a 'mistake' is always post-hoc. [...] Hence the differentiation of a perception from an illusion is a social distinction formed in consensus with others, (usually in conjunction with some authority who has an instrument). We believe the external source of authority.