278 THE EVOLUTION OF SCIENTIFIC THEORIES 



tertain the theory in a form that Dalton would have found unaccept- 

 able. From Faraday's distinctly physical concept of lines of force, 

 Maxwell extracts the sophisticated abstraction of the electromag- 

 netic field; and Maxwell's theory, like Newton's, is given its ultimate 

 expression by French formalists. Bohr's quantum theory is funda- 

 mentally syncretic ( the central derivation applies classical laws to a 

 markedly nonclassical system ) and it involves multiple auxiliary pos- 

 tulates of quantum numbers, etc. The theory is improved through 

 the work of Sommerfeld and others, and finally achieves its definitive 

 formulation in the quite differently slanted theories of quantum 

 mechanics. These theories at last offer fully self-consistent treatments 

 of nonclassical systems, and all the quantum numbers now appear as 

 necessary consequences of the more powerful sets of postulates. But 

 even these theories of quantum mechanics did not spring to being in 

 full perfection: for example, we now entirely reject Schrodinger's 

 original interpretation of the wave function. 



The magnitude and time scale of such refinements are extremely 

 variable: their net effect seems generally the same. The theory is 

 completed and perfected. Deploying now an absolutely minimal set 

 of postulates, it is recast in a form of absolutely maximal power and 

 generality. Certain exclusions, originally unavoidable, may now be 

 lifted. From the narrowness and crudity of its weak youth, the theory 

 grows toward the broad and subtle power of maturity. The phase of 

 consolidation shades into the phase of exploitation. 



Maturity. Where pioneers once trod hastily and at their peril, the 

 husbandman now tills the soil. The once-daring theoretic ideas are 

 now used routinely, and they impose on scientific research some 

 particular characteristic orientation ( s ) . Thus attention will be di- 

 rected toward certain phenomena, problems, and experiments and, 

 correspondingly, turned away from others that seem unimportant or 

 not susceptible to study. Work thus prosecuted under tlie guidance 

 of the theory will fully explore its consequences: all the i's will now 

 be dotted, all the t's crossed. And all the time strenuous efforts will 

 be made to stretch the theory, both in depth and in breadth. That is, 

 we demand that the theory ( perhaps originally based on quite crude 

 data) show its competence to construe the results of observations 

 and experiments we are forever improving in accuracy. And we de- 

 mand also that the theoretic pattern be extended into forever-new 

 domains of experience we regard as contiguous to those in which it 



