Teacher Learning in a Community of Practice: A Case Study of ...

analysis and that determinants ofsuccess ofthe deductions made are the laws of
rationality and the logic of choice. The concept of rationality in economics implies the
law that individuals always choose that option that is best, given the available knowledge:
Any individual in her economic life will never undertake action that adds more to her
losses than her gains. Choice behaviour is an essential characteristic ofeconomics and is
mediated by the effects ofscarcity and the need to act rationally. The discipline
economics has a distinct mode ofthinking and this distinct mode is embodied in its
dominant models. The mode ofthinking is deductive rationality in constrained
environments (Jeffreys 1987). Each key economic concept must have some element of
deductive rationality in constrained environments.
The key concepts (opportunity cost, efficiency and marginality) that make up the core of
economics may be described thus:
Opportunity cost is a prime example ofa deductive concept that organises other concepts.
It helps determine a set ofsubordinate concepts. The central assumption ofopportunity
cost is that each act excludes other possible acts at any given moment ofaction. It is a
necessary condition for the concept ofeconomic rationality. There is no economic
problem that does not involve the perspective that each alternative has a cost and that one
of these alternatives will have the least cost. The search method for the least cost is
essentially deductive.
The concept marginality derives its importance from the fact that the appropriate unit of
appraisal in relation to maximising economic behaviour is that ofthe increment. The
mathematics ofmaxirrtisation is a question ofmarginal analysis (where total revenue can
be equal to or exceed total costs without profits being maximised). Marginal analysis
allows the concept ofrationality"... to function dynamically in models. Marginal
thinking characterizes the psychology of a rational maximising agent" (Jeffreys 1987:23).
Efficiency in economics functions as a limiting concept. It is a way ofassessing the
operation ofother key concepts (marginal decisions must produce efficient results and the
cost ofdifferent opportunities is assessed through relative efficiencies). The concept is
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