

Table: Symmetry by three archetypes of scientific
theories Introduction: Although the nature of scientific theories can be either explanatory, predictional, exemplary or something in between these three archetypes (see below and click the names), the structure of such theories is always symmetrical in the sense that scientific theories are made up by an explanans produced by induction and an explanandum produced by deduction of explanans. See the covering law model. Note: All bold text in table
below can be clicked to obtain more information 

Quasisciences: E.g., economics 
Exemplary sciences: E.g., physics 

'the Machlup [1955] approach' 
'the Friedman [1953] approach' 

Explanans has to be found by empirical investigation of facts. This
is empirical
induction the strength of explanatory theory. 
Explanans is constructed by use of a few realistic
assumptions and many unrealistic but simplifying
assumptions. This is hypothetical induction
the weakness of predictional theory. 
Explanans has to be found by empirical investigation of facts. This
is empirical
induction one of the strengths of exemplary theory. 

Explanandum is made by use of wildly unrealistic but simplifying
intuition. This is intuitive
deduction the weakness of explanatory theory. 
Explanandum has to be found by algebraic manipulations of
mathematical models. This is logical deduction the
strength of predictional theory. 
Explanandum has to be found by algebraic manipulations of
mathematical models. This is logical deduction
one of the strengths of exemplary theory. 

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