of  the  sane  elements  extractable  from  the  motley  ore  of  ideas  referred  to  as  the  “anthropic 

principle”.) 



Since  this  point  confuses  many,  it  is  worth  expounding  it  slightly.  Consider  two  different 

hypotheses.  One  says  that  the  evolution  of  intelligent  life  is  fairly  easy  and  happens  on  a 

significant  fraction  of  all  suitable  planets.  The  oth er  hypothesis  says  that  the  evolution  of 

intelligent  life  is  extremely  difficult  and  happens  perhaps  only  on  one  out  of  a  million 

billions  planets.  To  evaluate  their  plausibility  in  light  of  your  evidence,  you  mu st  ask 

yourself,  “What  do  these  hypotheses  predict  that  I  should  observe?”  If  you  think  about 

it,  it  is  clear  that  both  hypotheses  predict  that  you  should  observe  that  your  civilization 

originated  in  places  where  intelligent  life  evolved.  All  observers  will  observe  precisely 

that,  whether  the  evolution  of  i ntelligent  life  happened  on  a  lar ge  or  a  small  fraction  of  al l 

planets.  An  observation  selection  effect  guar antees  that  whatever  planet  we  call  “ours” 

was  a  succe ss  story.  And  as  long  as  the  total  number  of  planets  in  the  universe  is  large 

enough  to  compensate  for  the  low  probability  of  any  given  one  of  them  giving  rise  to 

intelligent  life,  it  is  not  a  surprise  that  a  few  success  stories  exist. 



If—as  I  hope  is  the  case—we  are  the  only  intelligent  species  that  has  ever  evolved  in  our 

galaxy,  and  perhaps  in  the  entire  observable  universe,  it  does  not  follow  that  our  survival 

is  not  in  danger.  Nothing  in  the  above  reasoning  precludes  the  Great  Filter  from  being 

located  both  behind  us  and  ahead  of  us .  It  might  both  be  extremely  improbable  that 

intelligent  life  should  arise  on  any  given  planet,  and  very  improbable  that  intelligent  life, 

once  evolved,  should  succeed  in  becomin g  advanced  enough  to  colonize  space. 



But  we  would  have  some  grounds  for  hope  that  all  or  most  of  the  Great  Filter  is  in  our 

past  if  Mars  is  indeed  found  to  be  barren.  In  that  case,  we  may  have  a  significant  chance 

of  one  day  growin g  into  something  almost  unimaginably  greater  than  we  are  today. 



In  this  scenario,  the  entire  history  of  humankind  to  date  is  a  mere  instant  compared  to 

the  eons  of  history  that  lie  still  before  us.  All  the  triumphs  and  trib ulat ions  of  the 

millions  of  peopl es  the  have  walked  the  Earth  since  the  ancient  civilization  of 

Mesopotamia  would  be  like  mere  birth  pangs  in  the  delivery  of  a  kind  of  life  that  hasn’t 

really  begun  yet.  For  surely  it  would  be  the  height  of  naiveté  to  think  that  with  the 

transformative  technologies  already  in  sight—genetics,  nanotechnology  and  so  on—and 

with  thousands  of  millenn ia  still  ahead  of  us  to  perfect  and  apply  these  technologies  and 

others  that  we  haven’t  yet  conceived  of,  human  nature  and  the  human  condition  will 

remain  unchanged  for  all  future.  Instead,  if  we  survive  and  prosper,  we  will  presumably 

develop  into  some  kind  of  posthuman  existence. 



So  this  is  why  I  conclude  that  the  silen ce  of  the  night  sky  is  golden,  and  why,  in  the 

search  for  extraterrestrial  life,  no  news  is  good  news.  It  promises  a  potentially  great 

future  for  humanity. 



9