On studying futher I discovered that Ex 20 makes no reference to the Ten Commandments. The chapter simply begins "And God spoke all these words" and ends with thunder and lightning and the mountain smoking.

It is only when we get to Exodus 34 that we read about the Ten Commandments and the two stone tablets. However the commands God gives in Exodus 34 are not the usual Ten Commandments. They are listed in verses 14-26, and to summarise are:

1. Do not worship any other God
2. Do not make a treaty with those who live in the land.
3. Do not make cast idols.
4. Celebrate the Feast of Unleavened Bread.
5. The first offspring of every womb belongs to me.
6. Six days shall you labour but the seventh you shall rest.
7. Celebrate the Feast of Weeks.
8. Do not offer the blood of a sacrifice along with anything containing yeast.
9. Bring the best of the firstfruits of your soil to the house of the LORD.
10. Do not cook a young goat in its mother's milk.

Following these commands, the chapter continues (verses 28-28):

"Then the LORD said to Moses, "write down these words, for in accordance with these words I have made a covenant with you and with Israel." Moses was there with the LORD forty days and forty nights without eating bread or drinking water. And he wrote on the tablets the words of the covenant - the Ten Commandments".

I looked this up in some Bible commentaries and it appears that scholars generally recognise that there are two "versions" of the Ten Commandments. This one in Exodus (sometimes called the "Cultic Decalogue") and the more well-known Ten Commandments in Deuteronomy.

What is significant about this is that the Bible contains what is necessary for salvation. If there are two traditions about what the Ten Commandments are, then clearly knowledge of the Ten Commandments is not necessary for salvation.

We know that the Bible contains different textual traditions - for example Matt 19:17, Mark 10:18 and Luke 18:19 all give Jesus replies to the Rich Young Man:

"Why do you ask me about what is good?" (Matt)
"Why do you call me good?" (Mark)
"Why do you call me good" (Luke)

If someone said that our etermal life were dependant on knowing which was the "accurate" answer we would say they were wrong, because how is it possible to know? Similarly those who claim Christians should keep the Ten Commandments can be objected to on the grounds of "which ones?"

"But", someone may object, "what about the covenant with Israel? Surely the Jews had to know?" Not at all, the Jewish covenant required that all the law (TORAH) be kept, hence having two traditions for the Ten Commandments within the books of the law did not present a problem since all the laws were to be obeyed anyway.

For Christians it is different. Since the Bible has two traditions of the Ten Commandments - one in Exodus and the other in Deuteronomy - God cannot require Christians to guess which one they have to keep.