Introduction 



tinuous. When they knocked their fists on a table, they had no doubt 

 that that table was solid and without holes. The conception of vacuum 

 was repugnant to them, but a day came in 1643 when it became impos- 

 sible to duck it. Later the theory of gravitation and the wave theory 

 jeopardized the integrity of that vacuum. Later still the new atomic 

 theory broke the continuity of matter. It took almost a century to estab- 

 lish that theory on a sound basis and no sooner was it established than 

 the atoms disintegrated into smaller and smaller particles. For a short 

 time it had seemed as if the atoms were the only solid things left in the 

 vacuum, and then suddenly the vacuum was rediscovered within the 

 atoms themselves. It is not necessary to extend these remarks. Our 

 conceptions of the world structure were modified so often with increas- 

 ing frequency, that the wisest children of men hardly knew where they 

 were. 



The most revolutionary change of all and the one which might be 

 used above all others to define "modern" man concerns the very idea of 

 science or knowledge. It would take too long to describe how it came 

 about, for the revolution, deep as it was, was gradual. Between a sci- 

 ence ancillary to theology or to divine revelation and one aimed at dis- 

 covering the truth irrespective of consequences, the distance is prodi- 

 gious, yet it was bridged by an infinity of small steps. The man of 

 science of today loves the truth above everything else and is prepared to 

 sacrifice everything to his quest. He is not anxious, however, to discuss 

 epistemological difficulties with philosophers, because he is satisfied with 

 his own intuition of truth (vs. error) and with his experimental verifica- 

 tions of it. He knows that absolute truth is hopelessly beyond his reach, 

 but that he can come gradually closer to it by the method of successive 

 approximations. Coming closer implies the possibility of having to re- 

 ject old conceptions as well as that of accepting new ones, but the honest 

 man of science is ready for that and used to it, so much so that it does 

 not hurt him any more to have to abandon some of his ideas. That 

 is a part of the game which he is playing with so much joy. There are 

 no dogmas in science, only methods; the methods themselves are not per- 

 fect but indefinitely perfectible. There are no certainties in science, but 

 in a sense there are no doubts. Or looking at it from another angle 

 everything is doubtful except the feeling that the margin of error de- 

 creases gradually, asymptotically. The fact that that margin will never 

 be equal to zero does not disturb the man of science but causes him, if 

 he be wise enough, to be very humble. 



Men and women untrained in scientific training might believe that 

 the conception of science which I have outlined is simply a personal mat- 

 ter, somewhat like a personal religion, but it is much more. In spite of 

 its gentleness that conception prepares him who harbors it for the ac- 

 ceptance of the most shocking conclusions and the most revolutionary 

 deeds. 



Let us see what happened in the past. There has been much dis- 

 cussion apropos of the causes of the French Revolution. Some of the 

 causes were purely material, hunger and misery, others were spiritual. 



