CHARLES GLASS, the American journalist kidnapped in Lebanon two months ago, is out and safe. His return is a matter of great general relief, though it is also a sharp reminder that 20-plus other foreigners seized in Lebanon remain hostages. Mr. Glass, an Arabic-speaking journalist with good Shiite contacts, had believed it was safe to duck back into Beirut in June to work on a book. His ordeal ended only the other night when he slipped away from his captors under circumstances that allow him -- and his captors, if they so choose -- to say that he escaped on his own.

The hostage-takers are likely to come from the radical Iranians in the Hezbollah, or Party of God, who moved in at Syria's behest to help repel the Israeli invasion of 1982 and stayed at Ayatollah Khomeini's behest to serve his goal of advancing the Iranian revolution. As Americans came bitterly to learn, the Iranians are specialists in using hostages to manipulate Western policy and public opinion. In the glory days of this line of Iranian conduct, the ayatollah helped unseat one American president, Jimmy Carter, and actually drew another, Ronald Reagan, into sending Tehran arms.

The big change in the hostage context, however, lies not in the chastening of America or in the turning away from direct bargaining for hostages. It lies in a new political calculation by Syria, which decided to start contesting rather than facilitating the sinister influence that Iran wields in Lebanon through the Party of God. The Syrians were especially affronted by the kidnapping of Charles Glass, an event that took place not long after they had signaled their new policy by moving large numbers of troops from the hinterlands into the kidnappers' favorite hunting ground of West Beirut. Damascus objected not so much to terrorism, which it practices itself on occasion, as to the fact that someone else was taking hostages on turf it regards as being under its control.

Charles Glass went from captivity to Syria, whose officials handed him over with a flourish to his own government. President Reagan responded graciously by saying he was glad and grateful. The American thinking apparently is that it makes sense to give Syria every inducement to keep up efforts to reclaim the other hostages. Eight Americans and 14 men from other foreign countries are left.