The idea may seem preposterous. But Thanksgiving is a typical part of the targeted phenomenon known as ''civil religion,'' referring to generalized acknowledgments of the national heritage of faith in God that fit as many religions as possible.

However, nonbelievers, or followers of religions with many gods, or with no gods, could find reason to object, even while they enjoy roast turkey and an extra day off.

A federal appeals court accommodated just that sort of objection when it outlawed the popular phrase ''under God'' in the Pledge of Allegiance. The U.S. Supreme Court scrapped the ruling on technical grounds this year, but a future legal attack on the pledge phrase is anticipated.

Meanwhile, the Supreme Court is plunging into an equally emotional matter, the legality of the Ten Commandments displays on public property all over the nation.

Next year, the high court justices will hear arguments and rule on the memorials at the Texas state Capitol and the courthouses in Kentucky's McCreary and Pulaski counties. Church-state separationists have challenged many similar monuments in court.

The Supreme Court, whose own chamber features a carving of Moses holding the Ten Commandments, refused to hear an Indiana case in 2001, but finally decided to end the confusion. Four federal circuit courts have said commandments displays are legal while three have outlawed them as an unconstitutional ''establishment of religion.'' State courts also differ.

Opponents of displays complain that the commandments include explicitly religious demands about worshipping the one God. They also cite the Supreme Court's 1980 Stone vs. Graham ruling. In that case, a 5-4 majority said Kentucky public schools couldn't display the commandments because a 1971 court dictum barred government action that lacks ''a secular legislative purpose.''

On that point, display advocates agree with the 1980 dissent from William Rehnquist (now chief justice). He argued that the commandments have a ''secular significance'' due to their impact on the development of the West's legal codes.

The 1980 decision is also criticized in an important new conservative work, The Supreme Court and Religion in American Life (Princeton University Press, two volumes) by historian James Hitchcock.

To Hitchcock, the insidious intent of the Stone ruling was ''to insulate the public sector from all religious influence.'' He finds it significant that the court banished the commandments without even ordering the usual arguments and briefs, showing how firmly entrenched strict interpretation of church-state separation has become.

The biblical commandments are central to Judaism and Christianity, but U.S. Muslim leaders have raised no strong objections to displays, perhaps because the Quran also says that God gave the law to Moses and teaches the same principles, though not in a single passage.

A partial exception is the Bible's command to worship and avoid work on the Sabbath (Saturday, transferred to Sunday by Christians). The Quran doesn't require Muslims to stop work for the entire day of weekly worship, but otherwise has a similar dictum:

''When the call is proclaimed to prayer on Friday (the Day of Assembly), hasten earnestly to the remembrance of Allah and leave off business'' (62:9).

A Supreme Court ruling prohibiting the Ten Commandments displays could create a firestorm of the sort that was predicted if the court had scrapped ''under God.''

The displays do raise three scriptural conundrums:

l Which English translation of the Hebrew should be used, the Protestant King James Version, a more modern Protestant edition, or a Roman Catholic or a Jewish one? And why?

l If the commandments are numbered, which of the three systems for dividing them should be followed, that of Jews, of Catholics or of the Protestants and Orthodox?

l Which text of the Ten Commandments should be displayed, the familiar Exodus 20:1-17 or the slightly different restatement in Deuteronomy 5:6-21?