"Ye are the salt of the earth:
but if the salt have lost his savour, wherewith shall it be salted?
It is thenceforth good for nothing, but to be cast out,
and to be trodden under foot of men."
(The Gospel According to Matthew, Chapter Five, Verse Thirteen, words spoken by Jesus during the Sermon on the Mount)
What I'm thinking this passage means is this: Salt, generally speaking, had three attributes in the minds of Biblical folk: it is pure, it preserves, and it adds flavor. By calling his followers the "salt of the earth" Jesus was saying that a) they should be pure of heart, unstained from the world, b) they should preserve themselves from corruption, and in so doing, preserve the world from corruption, and c) they should allow their faith to bring flavor to their lives, and in turn bring flavor to the other people of the earth.

Now, "unstained" does not mean "separated" or "cloistered" -- this we know from James 1:22-27, in which it is clear that action is also a

necessary component of a moral lifestyle. "The Christian cannot withdraw himself from the world, but must keep himself unstained." James does not mention salt in this section, but his "Blessed is..." allusions, and general tone, put his words into the same context as the Sermon on the Mount. Anyway -- with those first seven words, Jesus basically defined his vision of the ideal lifestyle. Later on, the human tendency to over-organize kicked in, resulting in church, and these days the whole thing is pretty much falling apart completely. (Entropy !!)

Which brings us to the bit about losing savour. What does that mean? Salt does not lose flavor unless dilluted. A little research uncovered this tid-bit, though:

 apparently, in Palestine in those days, the ordinary oven was located outside the home. An oven was stone, with a floor of tiles. Under the tiles was a layer of salt, to retain heat. After awhile, this layer would "perish" and no longer do its job. So the tiles would be taken up, and the salt thrown on the ground. Then a new layer would be poured in and the tiles replaced. This happened on a regular basis and the people listening would've understood the image. This is a metaphor for the renewing nature of faith.

Elsewhere, in Mark (ch. 9, v. 40) we have this lovely variant on the same ideas, which I will close with today:

"Salt is good; but if salt loses its saltiness, how will you reseason it?
Have salt in yourselves and have peace with one another."