Why in Ephesians 4:15 is ἀληθεύω translated "speaking truth" rather than "being true"?

Question

The ESV translates ἀληθεύω as "speaking truth" whereas more literal translations like YLT translates it as "being true". Why is there a difference, especially as it impacts application (being lovingly truthful in speech only versus the whole of one's life)?

15 Rather, speaking the truth in love, we are to grow up in every way into him who is the head, into Christ, 16 from whom the whole body, joined and held together by every joint with which it is equipped, when each part is working properly, makes the body grow so that it builds itself up in love. (ESV)

15 and, being true in love, we may increase to Him [in] all things, who is the head -- the Christ; 16 from whom the whole body, being fitly joined together and united, through the supply of every joint, according to the working in the measure of each single part, the increase of the body doth make for the building up of itself in love. (YLT)

Answer 1

At first glance, ἀληθεύω is a denominative verb derived from the base of the adjective ἀληθής—“true” and the noun ἀλήθεια—“truth.”¹ Hence, it should mean “to be [the] truth” (or perhaps “to be true”). According to the LSJ lexicon, the Greek verb ἀληθεύω can mean both “to speak truth,” i.e. speak truthfully, and “to be true.”² However, it notes that the latter usage is consigned to [inanimate] things, whereas the former is typically used in reference to people (i.e., those who can speak).³

A.“-εύσω” X.Mem.1.1.5, al.:—speak truth, A.Th.562, Hp.Prog.15, Pl.R.589c; “περί τι” Id.Tht.202b: with neut. Adj., ἀ. πάντα speak truth in all things, Batr.14; “πολλὰ ἀ.” X.An.4.4.15; τὰς δέκα ἡμέρας ἠλήθευσε he rightly foretold . . , ib.5.6.18; ἀ. τοὺς ἐπαίνους prove their praises true, Luc.Ind.20; τοὔνομα `make good', Them.Or.1.4c.

2. of things, to be, prove true, “σημεῖα” Hp.Prog.25:—Pass., to be fulfilled, of conditions, “ἐπὶ τούτοις -ομένοις” X.Cyr.4.6.10, freq. in Arist.:—Act. of reasoners, arrive at truth, Id.Metaph.1062a25:—Pass., “ὁ λόγος -εύεται” is in accordance with truth, Top. 132b4, al.; ἀληθεύεσθαι κατά τινος to be truly predicated of . . , ib.132a31, al.: fut. Med. in same sense, EN1100a35, al.

In Eph. 4:15, since the participle ἀληθεύοντες is referring to people, then the ESV seems to render the proper English translation as “speaking truth” rather than “being true.”

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References

Goodell, Thomas Dwight. School Grammar of Attic Greek. New York: Appleton, 1902.

Liddell, Henry George; Scott, Robert; et al. A Greek-English Lexicon. 9th ed. Oxford: Clarendon, 1940.

Footnotes

¹ As suspected, confirmed by Goodell, p. 150, §417 a.
² p. 63
³ At least in the NT, if the author wishes to describe an individual as being true, the tendency is to use a conjugation of the verb εἰμί in conjunction with ἀληθὴς as predicate adjective (cp. Matt. 22:16: «οἴδαμεν ὅτι ἀληθὴς εἶ»—“we know that you are true”).

Answer 2

I would translate Ephesians 4:14-15 this way:

¹⁴ So that no longer should we be infants, tossed to and fro and carried about by every wind of doctrine after the cunning of men, with craftiness akin to the trickery of fraudulence; ¹⁵ but, speaking the truth ^{ἀληθεύοντες} in love we should all grow into him who is the head, Christ.

Details:

Paul is using ἀληθεύοντες in verse 15 to contrast what he has just said in verse 14, concerning "cunning" and "craftiness" and "trickery" and "fraudulence", which is not how he came to them -- preaching the unsearchable riches of Christ, according to the manifold wisdom of God; (Ephesians 3:8,10)

Paul also uses this word in Galatians 4:16 where he says:

therefore, speaking the truth ^{ἀληθεύων} to you, have I become your enemy?

ἀληθεύων (speaking the truth) refers to verse 13, where Paul said he came to the Galatians in weakness of the flesh, proclaiming the Gospel.

"Being true" is a nebulous notion that one might feel about him/herself in a worldly sense, but the truths of the Christian Gospel are absolutes. For example, Jesus is THE Christ, and THE Son of the living God, and THE Truth, and THE Way, and THE Life, and THE Good Shepherd, and THE Light of the world, and THE Bread of life, and THE Resurrection, and THE Judge of the living and the dead. So, "being true" in regard to the Gospel is about proclaiming the absolutes, and doing works befitting of them, to the glory of the Father which is in heaven.