Philip K. Dick, "Man, Android, and Machine" in The Shifting Realities of Philip K. Dick (Lawrence Sutin, ed.) page 213

My theme for years in my writing has been, "The devil has a metal face." Perhaps this should be amended now. What I glimpsed and then wrote about was in fact not a face; it was a mask over a face. And the true face is the reverse of the mask. Of course it would be. You do not place fierce, cold metal over fierce, cold metal. You place it over soft flesh, as the harmless moth adorns itself artfully to terrorize others with ocelli.