IS THERE INTELLIGENT LIFE ON EARTH? 



267 



1000 



1400 1800 



YEARS A.D. 



2200 



-1 1 



THOUSANDS OF YEARS 



Fig. 1 Population growth to date compared with a retrospective model of the 

 industrial era in historical perspective [inspired by Hubbert (1969), Fig. 8.27] . 



o 



D 

 Q 

 O 



QC 



Q_ 



3. Japan, which is pressing hard on our heels, and almost entirely with 

 imported materials. 



That sets the stage for considering just how far industrial civilization can 

 grow in any country or in the world at large without consequences that undo the 

 good it is capable of creating, given appropriate controls. 



Now a few words about concepts of optimum population and of quality of 

 life, both of which are involved in my thinking. Is there such a thing as an 

 optimal population, and, if so, what is it for different parts of the world and for 

 the world as a whole? How does one define "quality of life," which, in 

 concrete terms, surely means different things to different people? 1 would define 



