ABSTRACT
The function of theory is to give coherence to observations. What conclusions may be drawn from this coherence will vary with the data to which the observations refer, and with the rigour with which the theory may be constructed. The most effective theory is one which states precise relationships among precisely defined, quantified variables and which accordingly permits prediction of the outcomes from the specified interactions, with a very high degree of probability that the predicted events will in fact occur. Many theories in the natural sciences are of this kind, and within their limits their predictive capabilities are high. But their effectiveness derives from the possibility of defining the limits of the observations to which the theory refers without thereby excluding variables which are of significance.
