Former neurosurgeon Ben Carson rallied Republicans at the Iowa Freedom Summit on Saturday, stirring up speculation once more that the conservative activist will seek his party's presidential nomination next year. Carson has never run for office and only recently registered as a Republican, but as the author of six books over more than two decades, he does have a considerable paper trail—and it's starting to get him into trouble. In his 1992 book Think Big, for instance, Carson proposed a national catastrophic health care plan modeled on federal disaster insurance, which would be funded by a 10-percent tax on insurance companies.