However, the postulate of maximization when used alone is still useless for us to say anything on human behaviour because whatever a person does can be said to be selfish, i.e., maximizing his own interest only. A 'theory' that rests on this postulate alone is nothing more than a tautology and can never be refuted, and therefore is useless in explaining human behaviour.

Thus only if we can specify what particular behaviour will be resulted from the postulate of selfishness under a specific set of constraints, will this postulate be useful for us to predict or explain human behaviour. We must know the goal(s) of the 'selfish' individual. An economic model usually assumes one or some of the following as the goal of the individual such as the maximization of wealth, of utility and the minimization of risk. The specification of well-defined goal or objective, makes the theory more restrictive and therefore more powerful in explaining human behaviour.

Definition of Economics

Economics can be defined as a science which rests on the postulate of maximization or selfishness to explain or predict human behaviour, i.e., human choice among options. In order to explain and predict human behaviour, it is important for the theory to specify clearly what are the relevant constraints confronting a choice; and what people are exactly maximizing and what types of observable behaviour are implied by the goal(s).

Some Remarks on a Good Economic Theory

(1) A 'truth' is not a theory.

(2) A theory predicts rather than forecasts.

(3) Consistency with the axioms (or assumptions, postulates).

(4) A theory is necessary a simplification of facts.

(5)  Assumptions can be unrealistic but test conditions or constraints must be valid.

(6) A theory must be potentially refutable be facts.

(7) The greater the generality, the more powerful the theory is.

(8) Logical consistency is a must.