Hebrews 5:14 (Maturity, Solid Food, and Perceptive Faculties)

SBLGNT: τελείων δέ ἐστιν ἡ στερεὰ τροφή, τῶν διὰ τὴν ἕξιν τὰ αἰσθητήρια γεγυμνασμένα ἐχόντων πρὸς διάκρισιν καλοῦ τε καὶ κακοῦ.

The cooordinating conjunction that begins this verse in terms of translation (a postpositive particle) is δέ, which probably is adversative whereas the grammatical subject of ἐστιν is ἡ στερεὰ τροφή ("solid food"); by the article, we know that the noun phrase is grammatically feminine with respect to its morphology. See Going Deeper with NT Greek for a discussion of how Hebrews 5:14 transitions from 5:13.

τελείων is genitive plural masculine of the adjective τέλειος ("perfect, mature, complete, adult, full grown") and functions predicatively here (Zerwick-Grosvenor, page 664; Robertson, Grammar, page 497). Robertson calls τελείων, a "predicate genitive" (Word Pictures in the New Testament), and David Allen insists the word is fronted in order to make it emphatic (Hebrews in the NAC Series). Moreover, he severely criticizes the NIV handling of Hebrews 5:14, especially the latter part of the verse.

Going Deeper with New Testament Greek: "Here, τελείων functions substantively, in the slot of the predicate nominative. Yet, as a genitive, τελείων communicates possession. Solid food belongs to mature Christians."

Köstenberger, Andreas J.; Merkle, Benjamin L; Plummer, Robert L. Going Deeper with New Testament Greek: An Intermediate Study of the Grammar and Syntax of the New Testament (Kindle Locations 12385-12387). B&H Publishing Group. Kindle Edition.

Rogers and Rogers: "[τέλειος] refers to those who should assume adult responsibilities. The author is using terms of human development to describe the readers’ development in faith (Buchanan; BBC; for a parallel in the DSS s. 1QS 1:10-11)."

τῶν refers back to τελείων (Zerwick-Grosvenor), both are genitive plural masculine forms. Compare Going Deeper with New Testament Greek (Kindle Edition, Location 12389).

διὰ τὴν ἕξιν-William Lane explains that one can interpret ἕξις as referring to a state ("condition, capacity") or to a process ("exercise, use"). In other words, one could construe the term passively or actively. He cites Philo, Allegorical Interpretation of the Law 3.210 and The Prologue to Sirach. After weighing the options, Lane appears to favor the second sense: compare RSV, NEB, ESV and NET. One tipping point for Lane is the participle γεγυμνασμένα, which possibly favors the active sense.

For the potential meaning of ἕξις, see BDAG and John A. L. Lee. “Hebrews 5:14 and Ἕξις: A History of Misunderstanding.” Novum Testamentum 39, no. 2 (1997): 151–76. http://www.jstor.org/stable/1561248.

BDAG on τὰ αἰσθητήρια-αἰσθητήριον, ου, τό ⟦aisthētḗrion⟧ (Hippocr. et al.; Herm. Wr. 7, 3; Jer 4:19; 4 Macc 2:22; Philo) lit. ‘organ of sense’; fig. capacity for discernment, faculty, of the ability to make moral decisions (s. PLinde, De Epicuri Vocab., Bresl. Philol. Abh. X/3, 1906, 32) τὰ αἰσθητήρια γεγυμνασμένα ἔχειν πρὸς διάκρισιν καλοῦ τε και κακοῦ have one’s faculties trained to distinguish betw. good and evil Hb 5:14 (cp. Galen, De Dign. Puls. 3, 2 vol. VIII 892 K. αἰσθητήριον ἔχειν γεγυμνασμένον; Iren. 4, 38, 2 [Harv. II 294, 12] appears to have Hb 5:14 in mind).—DELG s.v. 1. ἀΐω. TW.

γεγυμνασμένα ἐχόντων-the first word is a perfect participle middle-passive accusative neuter plural; ἐχόντων is a present active participle genitive masculine plural and it's adverbially modified by the prepositional phrase διὰ τὴν ἕξιν. See Going Deeper with the New Testament (location 12391) and the Brill Dictionary of Ancient Greek entry for γυμνάζω, page 445.

Robertson's Word Pictures: "For this predicate use of the participle with εχω see Luke 13:6; Luke 14:19. 'By reason of use' one gains such skill." But see Paul Ellingworth, Hebrews, page 309.

πρὸς διάκρισιν καλοῦ τε καὶ κακοῦ-Most writers see the distinctions made here as moral categories. The Hebrew Bible undoubtedly shaped the writer's language for good and evil, but Harold Attridge says Hellenistic writings are closer parallels. See Attridge, Hebrews, page 161; B.F. Westcott (The Epistle to the Hebrews, page 136) cites Genesis 3:5; Deuteronomy 1:39; Isaiah 7:16. Compare Numbers 14:23 LXX.