The Duplicated Man, by James Blish & Robert A. W. Lowndes. Paul Danton was a member of a subversive political party which had an answer: make peace with Venus. But the only way to peace was through the overthrow of Security. And Danton had found the one weapon which could make Security's fall possible: the long-forgotten duplication machine. What if the top members of Security were kidnapped briefly, and then suddenly there were 5 of each? No government could endure such chaos.