Connotations of "Salt of the earth"

If a word or expression can be taken one of two ways, but you meant it as a compliment, chances are it will be interepreted as a compliment. If someone called me the salt of the earth, I probably wouldn't stay up at night tossing and turning, wondering if I had just been called a simpleton, and fretting because I should have been able to devise a clever, on-the-spot retort (such as, "Thanks – and you're the fertilizer of the earth").

Given that the phrase is usually used in a complimentary fashion (provided one has not "lost his saltiness"), I don't think you have to worry about an inadvertant insult. It might be worth mentioning that one author opined:

To call a person “the salt of the earth” remains one of the highest compliments that can be paid.
_{Source: Wick Allison, That's in the Bible?: The Ultimate Learn-As-You-Play Bible Quiz Book, 2009.}

However, I'd say that the phrase is more old-fashioned than contemporary, and it might strike a secular scientist as rather quaint.

Although I don't think you've insulted anyone, I'm not sure I can give a full-fledged recommendation to employ the compliment often.

Yes, "salt of the earth" would refer to one's moral goodness - but it's also a phrase that has class connotations: I think we are far more likely to compliment a hardworking labourer as "salt of the earth" than a well-educated white-collar professional. "Salt of the earth" had class connotations in Jesus's day (he was referring to fishermen), and I think that this survives in current usage.

The second definition in dictionary.reference.com is a "cultural reference":

salt of the earth in Culture

salt of the Earth definition

Basic, fundamental goodness; the phrase can be used to describe any simple, good person: “I like Mary: she's reliable, trustworthy, and straightforward; she's the salt of the Earth.” In the Sermon on the Mount, Jesus tells his followers, who are mainly fishermen and other simple people, “Ye are the salt of the Earth.”

The American Heritage® New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

This has a date of 2005, which might make it surprising if simple were to mean "simple-minded, stupid, feeble-minded", although it's possible that an earlier edition might have used the word in that sense. I would propose that simple here does not mean that; rather it means "uncomplicated, straightforward, not disingenuous".

The only thing that distinguishes the two definitions (really just one definition there, think again!) is the definite article.

He is a nice person, salt of the earth! --> stating the quality of the person. (def. 2)

On the other hand,
He is a nice person, the salt of the earth! --> denoting the person as a significant example/ paragon/ only case of the class. (def. 1)

I just used the term to describe two people I know who are sincere, honest, hard working and kind. It escapes me how this needs to exclude the educated or world wise people. I have known the latter who are also the salt of the earth. Perhaps the latter are simply more rare. Betsy