POLITICAL ILLUSIONISM - Op-Ed - NYTimes.com By James David Barber ; James David Barber, professor of political science and policy studies at Duke University, is author of ''The Presidential Character'' and ''The Pulse Of Politics.'' (The New York Times); Editorial Desk April 26, 1984, Thursday Late City Final Edition, Section A, Page 23, Column 2, 1002 words [ DISPLAYING ABSTRACT ] America is drifting into a mode of political thinking that is not only illusory but consciously, even proudly so. Both Republicans and Democrats alike are afflicted with this malady. President Reagan's indifference to reality is hardly news. His criterion of validity is drama, not empiricism. As David A. Stockman, Director of the Office of Management and Budget, once summed up the White House system: ''Every time one fantasy doesn't work they try another one.'' Mr. Reagan, told by a reporter that one of his favorite, endlessly repeated anecdotes - how a...