In holding American hostages in our Tehran Embassy, Ayatollah Khomeini's followers are violating a principle of diplomatic inviolability respected by civilized nations for 4,000 years.

The ancestors of the present Iranians, the ancient Persians, showed a decent respect for that rule. Herodotus relates how the Persian King Darius sent emissaries to Athens and Sparta to demand Persian control over land and sea -- or, symbolically, "earth and water." The Athenians responded by throwing the one group of emissaries into a pit and the Spartans threw the other into a well, telling them scornfully to carry earth and water to their king from those two places.

Herodotus speculates that Athen's subsequent destruction by the Persians may well have been in punishment for that insolent action. The Spartans suffered also, concluding, with the post hoc, propter hoc logic of classical mythology, that their mistreatment of the Persian envoys was the reason that favorable omens no longer resulted from their sacrifices. With remorse born of panic, they enlisted two youn noblemen volunteers to offer their lives in penance to the Persian King. But Xerxes, who had by then succeeded his father, Darius, rejected the offer with the disdainful comment, "Persians would not behave like the Spartans, who, by murdering the ambassadors of foreign power, had broken the law which all of the world holds sacred."

All that, of course, was centuries before Persia fell under the periodic sway of fanatical Shi'ites, who just 150 years ago displayed their contempt for the law "all the world holds sacred" by an action that, up to a point, remarkably parallels the current lamentable developments.

In 1828, a famous Russian satirical writer and diplomat, Alexander Sergeyevich Griboyedov, negotiated the Treaty of Turkmanchai, by which Persia ceded Georgia to the Russian Empire. Soon thereafter, the Russian government sent Griboyedov to Tehran as ambassador and "acting head of the Russian Embassy" to oversee the execution of the treaty.

In the course of his duties in Tehran, the new ambassador gave sanctuary in the embassy to several Georgian women who by the treaty had become Russian subjects. The fact that they had escaped from Persian harems and that he was thus challending an honored institution incensed fanatical Shi'ite leaders. The chief mujtahid (roughly equivalent to an ayatollah) denounced Griboyedov and demanded his death, announcing that Persians could legally rescue the refugee women from the infidel Russians.

Inflamed by these exhortations and acting with the apparent support of the shah (whose cousin was one of the most violent of the agitators), a mob of perhaps 100,000 stormed the Russian Embassy where Griboyedov was living. Though Griboyedov bravely mounted a defense, the mob killed not only his guards but the whole diplomatic mission and staff -- a total of 37. The mob then mutilated Griboyedov's body to the point where other Russian representatives could later identify it only by an old dueling scar.

Fearing the wrath of the Russian Empire, the shah did not respond in the manner of the Spartans by offering as penance the lives of two noblemen -- or even two noblewomen; instead, he gave the Russians a huge diamond from the famous Peacock Throne. That throne -- the ultimate in conspicuous consumption -- had been built for Tamerlane and was among the spoils taken by the fierce Persian conqueror Nadir Shah when he captured Delhi from the last of the great Mogul emperors -- a voluptuous monarch who was reputed never to have been "without a mistress in his arms and a glass in his hand." The stone turned over to the Russians -- which had become known as the "Shah Diamond" -- is now part of the collection in the Kremlin.

Since optimism is the only useful working hypothesis, one must assume that the world has made at least marginal progress since 1828 and that the hysterical rabble surrounding our embassy (it insults education to call them "students") will not physically injure the hostages. Nevertheless, the fact that fanatical Shi'ites have once again stirred up a mob to assault a foreign embassy, as they did a century and a half ago, suggests the inevitable excesses of a theocratic state -- and the dangers of ever entrusting political power to religious zealots. Since religious passions perverted into hatred acquire inhuman ferocity, it is not surprising that religious wars have been among the bloodiest in history; for when doctrine is expressed in violence, atrocities become sacramental.

Nations maintain peaceful relations with one another by constant compromises that reconcile one people's interests with another's. But dogmatic religions are based on too many absolutes -- and all too often their prophets are too intolerant to acknowledge the interests of others. Moreover, religion armed with powers of the state is a force without accountability since it recognize no manmade constraints.

At many times and in many places, bigots from Savonarola to the archbishop of Salzburg to Oliver Cromwell have destroyed freedom and placed stifling shackles on the boldest and noblest minds. Men of like tendency can also -- as in Iran today -- debauch a people by inflicting a whole nation the wild lunacy of mob action. Fanaticism is the dark face of religion and, in the words of the French encyclopedist, Diderot: "There is only a step between fanaticism and barbarism." In Iran today, Khomeini has taken the step.

For Americans the lesson should be clear: our founding fathers were inspired to insert into the First Amendment of the Constitution a clause forbidding the making of any laws "affecting the establishment of religion." That clause required the separation of church and state. Those few words are a heritage we must jealously guard.