Edgar Pangborn 
Mirror for Observers [EPUB ebook] 

The Martians, long exiled from their home planet, have for millennia been observers of the world of men. Forbidden by their laws to interfere with human destiny, they wait for mankind to mature.From the turmoil of mid twentieth-century America, word comes to the Observers that one of their renegades is hoping to encourage humanity in its headlong rush to self-destruction through corruption of a single rare intellect. The struggle between Observer and Abdicator for the continuance of the human species is one the classic conflicts in the annuals of science fiction.