172 GROWTH PRINCIPLES AND THEORY 2 



case; he was defeated in his later Hieracium experiments; and if he had started 

 with some complicated case in drosophila, involving sex linkage, coupling, 

 crossing over, position effect, etc., genetics would never have been founded 

 by him. 



Another important aspect of scientific theory is the unification of previously 

 disparate facts it provides. To the naive observer, the revolution of planets, 

 free-falling bodies, bodies rolling on an inclined plane, the swing of a pendulum, 

 ebb and tide, etc. have nothing in common. Yet these phenomena are united 

 by the laws of mechanics, and so are mechanical and thermal phenomena in 

 statistical mechanics, optical and electrical phenomena in electrodynamics, 

 crossing experiments and cytological facts in cytogenetics, etc. 



A further "dividend" is the verification of calculated constants by independent 

 experiment. For example, when Loschmidt calculated the number of molecules 

 in a gas per unit volume and under standard conditions, Loschmidt's number jV, 

 so long as this calculation stood isolated, could still be considered as a sort of 

 freak and the atomic structure of matter as fictitious, as was actually the case 

 with Mach, Ostwald, and other physicists. When, however, Loschmidt's number 

 came out the same in calculations so different as from kinetic theory, Brownian. 

 movement, radioactivity, etc., doubt in the calculated value of jVand the under- 

 lying theory became meaningless. 



In the above examples we have assumed that the initial model and theory were 

 well-chosen and productive of further development. There is, of course, no 

 guarantee for this being the case. History of science if full of misconceived theories 

 which did not stand the proof and were discarded. However, there is little need 

 to worry about wrong theories; they are quickly eliminated in the progress of 

 science. As a rule it may be said that a wrong theoretical model is better than no 

 model at all, as can be evidenced by many examples from the history of science. 

 A biological case to the point is Weismann's theory of "determinants" and 

 "unequal nuclear division" which was thoroughly wrong but formed the stepping 

 stone toward modern cytogenetics. 



One more aspect of scientific theory deserves emphasis in this connection. It is 

 often maintained that theory, models, and laws are impossible or premature 

 because the phenomena in question are too complicated and the underlying 

 processes too little known to allow them. This particularly applies to biological 

 phenomena such as growth which obviously are the outcome of innumerable and 

 largely unknown component processes. 



The answer is that nothing in nature is "simple" ; more or less "simple" are only 

 the conceptual models we devise to represent certain aspects of natural phe- 

 nomena. 



This question is intimately connected with the hierarchical stratification of 

 nature and what has been termed, in psychology, "molecular" and "molar" 

 theories. "Molecular" theory tries to advance analysis into components, "molar" 

 theory to state overall laws. In this respect, two general rules can be stated. 



I. Scientific progress, as a rule, is in the direction of resolving overall phenom- 

 ena into phenomena at lower levels, that is, from "molar" to "molecular" 

 research. This is evident, for example, in the development from "macro" to 



