For those seeking clues to the judicial philosophy of John G. Roberts, documents from his years as a lawyer in the White House counsel's office during the Reagan administration provide revealing evidence. in 1983, Mr. Roberts addressed a proposed constitutional amendment setting a 10-year term of office for federal judges. The Justice Department opposed the measure on the ground that life tenure was critical to judicial independence. Mr. Roberts did not disagree, but noted that the framers had adopted life tenure at a time when life expectancy was significantly shorter. He then made an argument in favor of limited terms. "Setting a term of, say, 15 years would ensure that federal judges would not lose all touch with reality through decades of ivory tower existence," Mr. Roberts wrote. "It would also provide a more regular and greater degree of turnover among the judges."