38 Introduction 



of observed universal constants and their value found by his "pure rea- 

 soning" was impressively close. And yet the undertaking frightens us 

 beyond words.^^ 



We must philosophize, but it is safer never to lose sight of experience. 

 We must go back to the concrete and tangible facts as often as possible 

 to keep our strength and our sanity. Like Antaeos we are safe only 

 as long as we remain in touch with the good earth. We must not extra- 

 polate too far; in such matters it is safer to imitate the plain terrestrial 

 physicists than the astrophysicists. With the disturbing exception of 

 Eddington, the majority of scientists of our time avoid superrationalism 

 and fantastic extrapolations. It is not that they are wiser than their 

 mediaeval ancestors, but centuries of experimental success and failure 

 have sobered their thoughts. In a curious way Eddington helps us to 

 be more tolerant with mediaeval scholasticism, for he shows us how diffi- 

 cult it is to follow the narijow road between irrationalism and excessive 

 rationalism. 



The mediaeval gestation was necessary; it would have had to occur 

 in one way or another. It might have been faster, but we cannot explain 

 why things happen as they do, and in particular their tempo defies analy- 

 sis; it is futile to consider imaginary sequences different from the real 

 ones. 



Young historians of science, who know only the bare outline as may 

 be read in a short primer, may fancy that the development of science was 

 much simpler than it really was; that it was logical, continuous, straight- 

 forward. Nothing is further from the truth. To begin with, the march 

 of science was often thwarted and deflected by general principles or 

 prejudices, not to speak of physical or human calamities ( such as earth- 

 quakes, epidemics, wars). The notion that the trajectories of planets 

 must be circular retarded Kepler's discovery for centuries, though Apol- 

 LONios had prepared the mathematical basis of it. That is tlie classical 

 example of inertia due to prejudice, but there are plenty of others. 

 Each great discovery of the past has been retarded by a similar inertia. 

 In a particular case that spiritual inertia is still blocking the way. I am 

 referring to the metric system. One of its two fundamental ideas^^ — 

 that the system of weights, measures and moneys should be built on 

 the same basis as our number system — was hit upon by Sumerian mathe- 

 maticians more than five thousand years ago. It was reasserted very 

 clearly by the Flemish mathematician, Simon Stevin in 1585. The 

 metric system was established in 1795.^'^ It has since been accepted by 

 the majority of civilized nations, but not by England nor America. 



*^For further discussion of this, see Max Born: Experiment and theory in 

 physics (44 p., Cambridge University Press, 1943; Isis 35, 261, 263) and Dingle's 

 inaugural lecture (1947). 



*^ The other one concerns the choice of units; the independent units should be as 

 few and as universal as possible. 



■'■'Sarton: The first explanation of decimal fractions and measures, together vi'ith 

 a history of the decimal idea (Isis, 23, 153-244, 1935). 



