LUCRETIUS 25 



order and motion changed, produce air ; and all 

 other things may in this way interchange with one 

 another." Illustrating this by the case of the 

 letters of the alphabet, he explains : " It matters 

 much with what other letters and in what order 

 the several letters are placed. If all the letters 

 are not entirely alike, still by far the greatest part 

 are ; but the words which they compose differ 

 through the position of these letters. Thus in 

 material things as well : when the clashings, 

 motions, arrangement, position, and shapes of mat- 

 ter change about, the things must change too." 



The weakest point about the atomic theory of 

 Lucretius is its failure to account for the con- 

 course and combination of the atoms. According 

 to theory, the atoms rain straight down through 

 the void. Raining straight down, they would never 

 clash, and meet, and combine ; so Lucretius has 

 to postulate that they occasionally swerve from a 

 straight line, and so collide. " This point of the 

 subject we desire you to apprehend, that when 

 atoms are borne straight downwards through the 

 void by their own weights, at quite uncertain times 

 and uncertain places they push themselves a little 

 from their course, only just so much that you can 

 call it a change of inclination. If they were not 

 wont to swerve thus, they would fall down like 

 drops of rain through the deep void, and no 



