LONDON — At this point it is clear enough who invaded Iraq. Contrary to general opinion, it was Iran. After all, applying the Roman principle of cui bono — “to whose benefit?” — there can be no question that Iran, the greatest beneficiary of the ousting of its enemy Saddam Hussein and the rise to power of Shiites in Baghdad, must have done it.

I know it appears that the United States was behind the invasion. What about “shock and awe” and all that? Hah! It is true that the deception was elaborate. But consider the facts: The invasion of Iraq has weakened the United States, Iran’s old enemy, and so it can only be — quod erat demonstrandum — that Tehran was the devious mastermind.

This mocking “analysis” is often deployed deadpan by my colleague, Robert Worth, the New York Times correspondent in Beirut. After three years living in Lebanon and crisscrossing the Arab world, he uses this “theory” to express his frustration with the epidemic of cui bono thinking in the region.

I say “thinking,” but that’s generous. What we are dealing with here is the paltry harvest of captive minds. Such minds resort to conspiracy theory because it is the ultimate refuge of the powerless. If you cannot change your own life, it must be that some greater force controls the world.