 Other theorists have challenged Burge’s assumption that they are committed to some form of representational liberalism. Schulte (2015) starts from Burge’s (2010) positive thesis that it is the possession of sensory systems with constancy mechanisms (e.g. size constancy, color constancy, shape constancy or motion constancy) that marks the distinction between representational and non-representational organisms. If that is right, Schulte argues, then there is a natural way for proponents of teleosemantics to incorporate that insight into their account: they can require producers of sensory representations to be systems with constancy mechanisms (where this is spelled out in a naturalistic   way)[24]   and maintain that non-sensory representations presuppose the existence of sensory   ones.[25]  By Burge’s own standards, such a theory would not be too liberal. An alternative non-liberal version of teleosemantics has been proposed by Butlin (2020a): he argues that sensory representations need not satisfy Schulte’s constancy-mechanism requirement as long as they have an ‘active consumer’, i.e. a consumer system where distinct processes are responsible for generating behavior and for coordinating behavior with environmental conditions.