Clearly No Distinction of Being
Your core question is "Did the Synoptic writers intend to convey any distinction between διάβολος and σατανᾶς?"
If by "distinction," you mean differing personalities (i.e. persons or beings), then I believe you have already answered your own question by noting the fact that Matthew and/or Luke uses διάβολος in places where Mark used σατανᾶς to refer to the same events and therefore the same being. To quote your comment:
Parable of the sower: Matt. 13:39 // Mark 4:15 // Luke 8:12. Temptation of Jesus in the wilderness: Matt. 4:1ff //Mark 1:13 // Luke 4:2ff.
Additionally, you have already noted as well in your original question that the LXX uses διάβολος in place of σατανᾶς in its translation of the Hebrew Scriptures. So the equation of the terms as a reference for the same being was already established prior to the writing of any of the gospels.
So the question must not really be about a distinction of differing personalities, as the evidence clearly points to an equation of the one personality involved being referenced by both words.
So Distinction of What?
Instead, the question really must be why was not a single designation used in the Synoptics (or any part of NT Scripture) to refer to this being? Or to recast the main question: What distinction did the Synoptic writers intend to convey between διάβολος and σατανᾶς? That is, if not a distinction of the personality of Satan, why use a different term in some, but not necessarily all, cases?
Certainly the choice of the LXX translators to use the translation διάβολος rather than to transliterate σατανᾶς had some influence on the gospel writers, for at the least it was an earlier equation of the words used to reference the same being.
But since two of the gospel writers do interchange the usage of the terms, do they intend any distinction in the passages since they choose to use one versus the other designation?
I think Cale's answer, while severely deficient in argument, is on the correct track. The term διάβολος, besides being a native Greek term (rather than a transliteration of a Hebrew term and thus a term that may have to be explained to Gentile Greek speakers), conveyed a specific type of adversarial relation, a slanderer. Now here we need to look at an English definition to help know what the Greek lexicons mean in their English definition of the Greek term. The Oxford dictionary definition of slander is:
The action or crime of making a false spoken statement damaging to a person’s reputation
So διάβολος is an adversary that works by means of not merely accusing (or generally opposing), but while accusing is also lying about the one accused. Why did the LXX translators choose this term? Because of the Hebrew Scripture context and the desire to be more explicit.1
The book of Job uses the term the most (which book I and many others take as one of the oldest of the writings found in the Hebrew Scriptures, but its dating is debated). Note the context of use in that book:
- Job is already declared righteous by the writer 1:1) and this is declared to be YHWH's opinion of him (1:8), even after the first round of testing (2:3).
- But Satan says otherwise than God of Job (1:9-10, 2:4-5).
We are even told in 2:3 that God rebukes Satan, stating "although you [Satan] incited Me against him [Job], to destroy him without cause" (NKJV; emphasis added). From God's perspective, Satan was slanderously accusing Job, not just factually accusing him. So for the LXX translators here, διάβολος was an excellent choice for a contextual translation of the Hebrew שָׂטָן.
The context in Zech 3:1-5 also shows that Satan's opposition was unfounded against Joshua the high priest, for Satan was rebuked for his opposition (v.2).
The use of διάβολος in 1 Chr 21:1 would be a forgone conclusion by the LXX translators since the more detailed passages mentioning Satan they had already determined διάβολος was a good translation. Arguably, the idea of slander is much further in the background of 1 Chr 21:1, and so the context there alone would not have lent itself as well to choosing διάβολος if that verse were in isolation.
Yet even so, the context still suggests an idea of slander. Joab's reaction to David was this in 1 Chr 21:3 (NKJV):
And Joab answered, “May the LORD make His people a hundred times more
than they are. But, my lord the king, are they not all my lord’s
servants? Why then does my lord require this thing? Why should he be a
cause of guilt in Israel?”
Joab's reply clues the reader in that part of the apparent reasoning that David called for the census was to find out who was really his servants. That is, David had likely been recipient of some type of slanderous reports about the people of Israel (i.e., the moving of Satan), and wanted an accounting of who was really on his side. Joab tried to assure him all the people were, but David insisted on continuing. So even in this passage, Satan's work is hinted to have a slanderous aspect in making David doubt the congregation of Israel.2
So back to the question of what may be intended by the distinction for the gospel writers. Three main ideas come to mind, but I lean toward the last the most:
- Obviously, it could be purely stylistic—for variety. Matthew and Luke may simply have chose to switch between terms to help with the monotony of using one term. In this case, no real "distinction" at all is intended; διάβολος is purely a translation of שָׂטָן when they desired to put the translation rather than the σατανᾶς transliteration. I consider this to be the least likely option.
- Building on #1, they may have chosen to use both terms with the idea that two audiences were in view: those more familiar with Hebrew and those more familiar with Greek, or at least more familiar with Hebrew scripture or the LXX translation thereof. The interchange of the usage would broadly help each group to key to the fact that this is the same creature being discussed. It both maintains the Hebrew term via transliteration, while continuing the LXX tradition of using the more explicit διάβολος to correctly note the idea of slander in the adversarial role of this being.
- Building on #2, it may be that Matthew and Luke switch between the two terms intentionally to more specifically emphasize (rather than broadly, as #2 holds) a distinction between the adversarial role more generally (σατανᾶς; Satan) and the slanderous role in that adversarial role more explicitly (διάβολος; Devil) in the particular passages. However, closer examination indicates this may have a nuanced purpose, and so...
Building on #3, there is a definite preference (not 100%) in Matthew and Luke to use διάβολος in their own narration and σατανᾶς when Christ is speaking. This indicates that σατανᾶς was primarily what Christ used and they are simply reporting that, whereas διάβολος is their own preferred way to refer to Satan. Note the evidence:
- Satan (σατανᾶς) used only in Christ's speech: 4:10; 12:26; 16:23.
- Devil (διάβολος) used in author narration: 4:1, 5, 8, 11 (the only use of Satan in chapter 4 is in the direct address spoken by Christ in v.10). Christ
- Devil used in Christ's speech: 13:39; 25:41.
- Satan used in Christ's speech: 4:8; 10:18; 11:18; 13:16; 22:31.
- Satan used in author narration: 22:3.
- Devil used in author narration: 4:2, 3, 5, 6, 13 (again, Satan used in this passage only in the quotation of Christ's direct address).
- Devil used in Christ's speech: 8:12.
- Satan used in Christ's speech: 3:23; 3:26; 4:15; 8:33.
- Satan used in author narration: 1:13.
So if Matthew and Luke prefer Devil in narration, and Christ apparently preferred Satan in his speech, any clue to the distinctive use would reside in the atypical uses.
Let us start with Luke. Why would Luke choose Satan over Devil in narration at 22:3? I think the answer goes back to the base distinction of #3, that when Satan enters Judas, it is not for purposes directly related to slandering, but directly opposing Christ through betrayal. So διάβολος does not fit the context.
Both Luke (8:12) and Matthew (13:39) report Christ in his explanation of the parable of the sower as using "devil," rather than Satan; while Mark still uses Satan (4:15). This is the only place in Luke Christ is said to use the term, and one of only two in Matthew. Context shows that #3 idea likely holds, for the word of God is what is sown, and the use of "devil" strongly hints that the removal of the word from the hearts of the hearers is by means of slander. Mark's use of Satan is either because he preferred only that term (arguably the case) and so changed it, or that Christ had perhaps said something like "that devil, Satan, comes and...," so Mark chose one word, Matthew and Luke another.
Matthew's other place where Christ uses devil is in 25:41, where Christ says "the everlasting fire prepared for the devil and his angels." Context again warrants Christ's switch based on the #3 proposition, for the punishment is linked to the activity (slander) by using "devil," which activity also relates to "his angels" (i.e. his messengers... those who carry his slander abroad).
So #4 appears the most likely explanation to me. Christ normally used Satan as the designation, as a name, but occasionally wished to focus on his activity of slandering. Narrators that did use devil normally were focused on his activity (the bulk in the temptation passage of Christ, where Satan is slandering God's ways and word), but Luke also used the term in the one place where slander was not the main form of opposition.
It is evident that no distinction of being is present in the exchange of terms. If the variation is not simply a variation for stylistic purposes between using translation and transliteration, then the distinction is either
- intended to help the audience broadly to equate the Greek idea of διάβολος to the Hebrew שָׂטָן based on the contextual evidence from the Hebrew scriptures that such is a good translation for his activities, i.e. that the Satan is a slanderer, or
- intended to specifically emphasize slander in the passages where διάβολος is used, without meaning to lose the adversarial idea (since slander is that) and yet without meaning to indicate a different being is in view either, or
- intended to reveal Christ's preference for using Satan and those narrators preference for using the descriptive devil, but still with sensitivity to switching as appropriate for context as #2 postulates.
Having analyzed the passages more carefully, I think #3 is very sustainable as to what the distinction intended was for Matthew and Luke.
1 The word שָׂטָן does not of itself carry the idea of slander as the Greek διάβολος does, for YHWH Himself is the satan, the adversary, in Num 22:22, 32. Nor does שָׂטָן necessarily carry the idea of a verbal opposition, like διάβολος, also seen in the Num 22 passage, but as well from the Philistines fear of David becoming so in the midst of battle in 1 Sam 29:4. So διάβολος ends up being a very specific Greek word that functions well to refer to the lying nature of Satan's verbal opposition, which is what the Hebrew scripture context so clearly reveals (as noted above in the main argument following this footnote).
2 I will relegate to the footnotes the fact that the non-explicit equation of Satan with the serpent in Genesis 3 by the Hebrew Scriptures is made explicit in the NT (Rev 12:9, 20:2), albeit also by the non-synoptic writer John (another reason to just footnote it).
However, if one holds, as I do, the unity of the Scriptures and that they are all given by God (i.e. dual authorship of man and God via inspiration), then the equation is unquestionable. Context, however, in Genesis 3 shows that the serpent acts in a διάβολος and σατανᾶς role, slandering God's character by refuting God's statement (the end of 3:4 is directly a lie from what God had said in 2:17). So the NT equation to the serpent by John is justified not only from being inspired by God, but also in the contextual match to what the serpent did. Again, this relates to the synoptics simply in that John in Revelation makes a clear statement that equates διάβολος, σατανᾶς, ὄφις (serpent), and δράκων (dragon).
John's gospel also shows Christ emphasizing the lying aspect of the devil (Jn 8:44 NKJV):
You are of your father the devil, and the desires of your father you
want to do. He was a murderer from the beginning, and does not stand
in the truth, because there is no truth in him. When he speaks a lie,
he speaks from his own resources, for he is a liar and the father of