 Unlike positivism, which conflicts with science by taking experiences as unanalysable building-blocks, realism treats experiences as analysable, explaining them as the result of processes not immediately accessible to observation. Experiences and observation-statements are thus revealed as more complex and structured than positivism had realised. Feyerabend over-extended the contextual theory of meaning to apply not only to theoretical terms but to observation terms too, arguing that there is no special “problem” of theoretical entities, and that the distinction between observation terms and theoretical terms is a purely pragmatic one. If, as the contextual theory also implies, observation-statements depend on theoretical principles, any inadequacy in these principles will be transmitted to the observation-statements they subtend, whence our beliefs about what is observed may be in error, and even our experiences themselves can be criticised for giving only an approximate account of what is going on in reality. All our statements, beliefs and experiences are “hypothetical”. Observations and experiments always need interpretation, and different interpretations are supplied by different theories. If existing meanings embody theoretical principles, then instead of passively accepting observation-statements, we should attempt to find and test the theoretical principles implicit in them, which may require us to change those meanings.