How do the Soviets view détenteas permanent peaceful coexistence? As a way of maintaining East-West balance? As a tactic to lull the West into relaxing its vigilance? Foreign-policy experts have been debating this issue since the early 1970s, when Washington and Moscow proclaimed their intent to work for a reduction of world tensions. Although taking a hopeful view of the long-term trend of U.S.-Soviet relations, Henry Kissinger has recently warned Americans against expecting too much of détente, which Kremlin hard-liners have long described as a mere tactic. Last week Soviet Party...