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Century saw his theories under attack from several quarters. What follows is a discussion of challenges to his account of the development of the object concept. Usually characterised as cognitive constructivist, Piaget’s theories are fully neither nativist nor empiricist (Lamb, Bornstein & Teti, 2002; Overton, 2003) but closer to the latter than the former (Carey & Markman, 1999). Although Piaget’s commitment to invariant stages might seem to imply an innate developmental programme he was clear that they were the necessary outcome of interactions between maturational processes and the experiences children have. The stages are universal because the world is as it is and because all children bring the same set of tools to bear upon it. Piaget conceived of children as systems with an equilibriating tendency. Disequilibrium results when experience contradicts internal representational structures (Sugarman, 1990) and drives the reorganisation and extension of representations to accommodate the disequilibriating experiences (Feldman, 1994). Development, then, is a process by which the child comes to represent the world and its logic with increasing accuracy (Thelen & Smith, 1994). The interdependence of mental structures causes internal representations to organise themselves int