Mat 5.13 reads as follows:

Ὑμεῖς ἐστε τὸ ἅλας τῆς γῆς· ἐὰν δὲ τὸ ἅλας μωρανθῇ, ἐν τίνι ἁλισθήσεται; εἰς οὐδὲν ἰσχύει ἔτι εἰ μὴ βληθὲν ἔξω καταπατεῖσθαι ὑπὸ τῶν ἀνθρώπων.

You are the salt of the earth. Now if the salt becomes bland, with what will it be salted? It is not good for anything anymore except being cast out to be trampled by people.

Compare this to the parallel in Luke 13.34-35:

34 Καλὸν οὖν τὸ ἅλας· ἐὰν δὲ καὶ τὸ ἅλας μωρανθῇ, ἐν τίνι ἀρτυθήσεται; 35 οὔτε εἰς γῆν οὔτε εἰς κοπρίαν εὔθετόν ἐστιν, ἔξω βάλλουσιν αὐτό. ὁ ἔχων ὦτα ἀκούειν ἀκουέτω.

Therefore, salt is good: but if even the salt becomes bland, with what will it be seasoned? It is suitable neither for the ground nor the dung heap; they throw it out. The one who has ears to hear, hear!

These two sayings are parallel in many respects. An interesting difference appears in the way each writer presents the things saltless salt is not good for. Luke uses a simple statement, “it is not fitting for the ground or the dung heap,” emphasizing its general uselessness. Matthew’s version, by contrast, is interesting in the way it is structured.

The except in Matthew 5.13

Matthew’s Jesus could easily have said, “salt that loses its saltiness εἰς οὐδὲν ἰσχύει (is good for nothing),” and left it at that. That is not what he says, though. He adds an except clause: εἰ μὴ βληθὲν ἔξω καταπατεῖσθαι ὑπὸ τῶν ἀνθρώπων. This is a rhetorically marked way to say what he is saying. Compare to the usage here in Matt 11.27:

  • Πάντα μοι παρεδόθη ὑπὸ τοῦ πατρός μου, καὶ οὐδεὶς ἐπιγινώσκει τὸν υἱὸν εἰ μὴ ὁ πατήρ, οὐδὲ τὸν πατέρα τις ἐπιγινώσκει εἰ μὴ ὁ υἱὸς καὶ ᾦ ἐὰν βούληται ὁ υἱὸς ἀποκαλύψαι.
  • Everything has been given to me by my father, and no one knows the son except the father, no one knows the father except the son, and whoever the son desires to reveal him to.

The basic assertion is: “The son is the only one who knows the father and the father is the only one who knows the son.” These assertions are presented in a marked pattern. First, there is a total denial of the category, “no one,” which is followed by the single exception, “except,” introduced by the phrase εἰ μή. This is not an uncommon pattern to come across in the NT. It is marked in that it puts extra focus on the one exception to the pattern.

Here are a couple more examples from Matthew just to demonstrate the same pattern:

  • Matt. 12:4 πῶς εἰσῆλθεν εἰς τὸν οἶκον τοῦ θεοῦ καὶ τοὺς ἄρτους τῆς προθέσεως ἔφαγον, ὃ οὐκ ἐξὸν ἦν αὐτῷ φαγεῖν οὐδὲ τοῖς μετ’ αὐτοῦ εἰ μὴ τοῖς ἱερεῦσιν μόνοις;
  • And how did he enter into the house of God and they ate the bread of the presence, which it was not lawful for him to eat, nor for those with him, except only the priests?

Put in a less marked way: “It is only lawful for the priests to go into the house of God and eat the bread of the presence.”

  • Matt. 12:24 οἱ δὲ Φαρισαῖοι ἀκούσαντες εἶπον· οὗτος οὐκ ἐκβάλλει τὰ δαιμόνια εἰ μὴ ἐν τῷ  Βεελζεβοὺλ ἄρχοντι τῶν δαιμονίων.
  • Now the Pharisees, having heard, said: “This one is not driving out demons except by Beelzeboul, the Prince of Demons.”

Put in a less marked way: “This one drives out demons by Beelzeboul, the Prince of Demons.”

These examples demonstrate how εἰ μή phrases usually work: state an on overly strong position which is not true until the except portion of the clause is added. In each of the above cases, the original statement is false—“no one knows the father,” “he is not casting out demons” (the example with David is less clear though the basic mechanics remain the same—the exception clause indicates the class for whom the statement is true in a heightened way). It is with the addition of the marked “except” portion of the clause that the whole statement becomes true.

In statements which follow this pattern. then¸ the except portion is crucial to the meaning. The entire import of the saying cannot be understood until the except portion is processed at the end. There is an element of surprise, as it were, thrown in at the end which forces the hearer to quickly rethink the entire expression.

What is saltless salt good for?

So, in Matthew 5.13 what is saltless salt good for? R. T. France writes:

The trampling of the tasteless “salt” does not have to imply that it then finds a useful role as surfacing for a path; it is simply thrown out into the street as refuse.

The Gospel of Matthew, The New International Commentary on the New Testament (Grand Rapids: William B. Eerdmans, 2007), 175.

While this may be the case, if that is the intention it is odd that the marked syntax, which usually puts emphasis on the except element, is used here. The marked syntax leads to an expectation that the εἰ μή portion is significant for the meaning of the whole negative expression. Following the normal pattern, we expect that “it is good for nothing” is actually an overstatement which becomes true only when the qualifying “except for” is added.

If the basic idea of “you are the salt of the earth” saying is that Jesus’ disciples are to be a flavor (of wisdom) and preservative to help keep the world from corruption, the syntax here suggests a further contribution of the saying in its Matthean form. It suggests there is a positive use for salty salt and a negative use for saltless salt (but a use nonetheless).

Salt of the earth vs. Salting the earth

The main point of this post has been to engage the syntax. The syntax gives an invitation to consider a more complex meaning of the saying than just focusing on the positive. The largely parallel saying about “light of the world” in v. 14-16 does not include a similar negative emphasis, so I don’t think we should make too much of this one here. But even in the following “light of the world” saying, it is fair to assume that the absence of light is inherently a bad thing, not just a useless state.

My preliminary thought here is that “except to be trampled underfoot” is meant to echo the idea of judgement in some form or another. Why use a marked syntax to just reinforce that saltless salt is not good for seasoning? A meaning like, “saltless salt is good for using as pavement on the path,” seems a rather bland thing to say in a marked way.

I wonder if the background here is more the practice of salting a conquered city. In the OT, Abimelech salts Shechem after destroying it (Judges 9.45). The practice was known in the Ancient Near East more broadly, even if not entirely clear in terms of symbolism. Perhaps the idea of Jesus’ statement here works something like this:

As the salt of the earth, you will be doing something: either good for the earth, or destructive towards it.

Within a sort of “two ways” understanding, if salt is good and light is good for the world, then saltless salt and the absence of light is inherently bad for the world–not just inconvenient or useless, but bad. Verse 13 may just make that implication clear(er).