22 SCIENTIST 



the experiment wouldn't be conclusive, since Aristotle and 

 his colleagues would reply that it is not any particular 

 oak but only the idea of an oak which is really the final 

 cause. The idea of an oak is outside the reach of experi- 

 mental techniques so there is no point in thinking about 

 it from the scientist's point of view. Like immortality and 

 the relative beauty of pictures, the idea of final cause has 

 become a pseudoquestion. 



Most people who speak of cause and effect are not 

 thinking of final causes but of what Aristotle classified as 

 primary causes. A classical example is found in the effect 

 on billiard ball B when it is struck by billiard ball A. 

 Surely science is concerned with this kind of cause, isn't 

 it? The answer to this question is not nearly so clear as 

 you might expect. What science in effect does is to assemble 

 information about the past and present and use this to 

 predict the future. Obviously this procedure involves some 

 assumptions about how the past is related to the future. 

 These assumptions, in turn, are much closer to the idea 

 of primary cause than to the final causes discussed above. 



Nevertheless, it has been known for a long time that it 

 is at least very difficult and probably impossible to be 

 absolutely sure that one event causes another. The usual 

 attempt to discover such a relation is based on observing 

 event A and noting that it is followed by event B. The seven- 

 teenth-century French scientist and philosopher, Descartes, 

 employed a homely example to suggest that there might 

 be something wrong about this procedure. He pointed out 

 that it would not be difficult to arrange two clocks in such a 

 way that one always struck the hour just a little before 

 the other one did. If we observed this phenomenon for 

 several days, it would be natural to expect in the future 

 to hear clock B strike soon after we heard clock A. It 

 would be almost as natural to say that the striking of 



