The Art of Tetman Callis

“The choice among alternative hypotheses equally consistent with the available evidence must to some extent be arbitrary, though there is general agreement that relevant considerations are suggested by the criteria ‘simplicity’ and ‘fruitfulness,’ themselves notions that defy completely objective specification. A theory is ‘simpler’ the less the initial knowledge needed to make a prediction within a given field of phenomena; it is more ‘fruitful’ the more precise the resulting prediction, the wider the area within which the theory yields predictions, and the more additional lines for further research it suggests. Logical completeness and consistency are relevant but play a subsidiary role; their function is to assure that the hypothesis says what it is intended to say and does so alike for all users—they play the same role here as checks for arithmetical accuracy do in statistical computations.” – Milton Friedman, “The Methodology of Positive Economics”