One of the criticisms of standard teaching practices is that they support merely "ritual" as opposed to "principled" knowledge (Edwards & Mercer, syntax but not semantics (Hull, 1985) or, similarly, semantically debased or pseudo-structural conceptions rather than meaningful constructions (Cobb & Yackel, 1993). Using the appropriation metaphor, Ernest (1991) makes a comparable distinction between knowledge owned by the teacher and knowledge owned by the pupil: while the ideal might be knowledge owned by the pupil, the reality frequently is ownership by the teacher. Thus Vygotskian and neo-Vygotskian approaches construction of knowledge such as Edwards and Mercer's (1987) and Mercer's later work (1994, 1995) maintain that the shaping of "principled" knowledge relies on the continuous production of shared mental contexts or frames of reference culminating handover of competence from guide to apprentice (cf. Rogoff, 1990). Context by this definition, is a property of the of situation which is jointly negotiated or constructed by the participants. For Edwards and Mercer and many others, "principled" knowledge is something to be aimed at as quality" knowledge versus empty syntactic rule-following. Their most illuminating example comes from an example of a group of secondary school students' failure, in a lesson on pendulums, other issues in scientific method, that of controlling variables (i.e. allowing only one at a time to vary) and their acquisition instead of knowledge which is embedded in the trappings of the lesson ("You couldn't have us all doing the same thing, so we/there was three of us and there was really three things to change on the pendulum so we done one each"). We can say, then, that a "principled" knowledge when she shows power to project from what has been learned in the past to appropriate and correct behavior in a variety of new and previously unencountered situations: in a new situation, she knows how to proceed.