General Observations on Forming the Model

Sackville-West. The Land, Summer, in Collected Poems. London Hogarth Press, 1933. 

9 A spontaneous lecture on the analogy between imagery and the dimensionless parameter is something my friends have learned to endure with a grace for which I am thankful. Because it is to be found in the papers here reproduced [277 = P, 308 = Q], as well as in others [J, K ], it will only be mentioned in passing. 

Little Gidding, in Four Quartets (New York, 1943). The relationship of ends and beginnings is a recurrent theme in Four Quartets. 

Although the model may be worked on in isolation and, as a system of mathematical equations, has a life of its own, it is at all stages part of an ongoing analysis of some other entity. This is sometimes represented as a commutative diagram in which the state of the nonmathematical (let us call it physical, for definiteness) system, S, is mirrored in the model, 2, by the modeling relationship h. Changes in the physical, say, Si - S2 = gS, are mirrored in the model as — 22 - The model is satisfactory if the di- 

In my preliminary definition, I mentioned the exterior purpose, and the use of the words model and simulation speaks to the respective purposes of conceptual understanding and actual approximation. Different models may be appropriate to the same purpose, and function best in different regions of parameter space. [See J (pp. 18-22) for a further discussion of this point.] 

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