You may be surprised to learn there was debate on this topic from at least the high middle ages. A quick Google search found this write up, which seems to be a

You may be surprised to learn there was debate on this topic from at least the high middle ages. A quick Google search found this write up, which seems to be a pretty good summary. http://vox-nova.com/2009/10/10/on-multiple-worlds-and-multiple-incarnations-some-speculation-following-st-thomas-aquinas-and-c-s-lewis/ http://vox-nova.com/2009/10/10/on-multiple-worlds-and-multip... EDIT: This is quite good too: http://www.unav.es/cryf/extraterrestriallife.html http://www.unav.es/cryf/extraterrestriallife.html