The fingernail sliver of metal that American officials say links Libyan agents to the Lockerbie bombing of 1988 would hardly convict in a fair trial. As Oklahoma City showed, a very few nonexperts can produce massive damage. Terrorists almost always have two motives in mind - revenge and policy change. And, sometimes, the minds that hold those ideas are truly sick. Americans and Israelis are quick to make that diagnosis for home-grown terrorists, but slow to allow a mental excuse for foreigners.
Suicide bombers seem motivated more by hatred than by hope for a changed future.
On the other hand, Iranian students who seized the US Embassy in 1979 wanted us to abandon the shah. If loathing for America had driven them, the hostages would never have emerged alive. Terrorism specialists immediately focus on Arab or Iranian groups. Any sheikh who has issued an outrageous threat or any action that might anger fanatics is interpreted as a probable cause. But it would plainly dilute the message to send it from so remote a site rather than from the front lines of the struggle against Israel.