who, though he was in the form [morphe] of God, did not count equality with God a thing to be grasped (Philippians 2:6 ESV).
And the Father who sent me has himself borne witness about me. His voice you have never heard, his form [eidos] you have never seen, (John 5:37 ESV)
In English, both μορφῇ and εἶδος are translated as 'form.' Are they synonyms?
What is the difference between the μορφῇ of God and the εἶδος of God?
The understanding of these words are heavily influenced by Greco-Roman philosophy and can be illustrated in Plato's Allegory of the Cave. In this allegory, Plato uses his metaphor to help us better understand his Theory of Forms.
In Plato's theory, εἶδος (eidos) represents the "Visible Form" while, μορφή (morphē) represents the "shape". Additionally, within Greco-Roman philosophy, there were also the φαινόμενα (phainomena), "appearances" which underwent significant philosophical discussion but are not particularly germane to the OP's question.
In Plato's allegory, Plato asks Glaucon to imagine a prisoner in the cell of a cave. Out of view of the prisoner is a light source. This light source illuminates an object - again out of view of the prisoner. The prisoner in the cave is only able to see the shadow cast by the object:
In terms of the Allegory, the εἶδος (eidos) is the object or vase while the μορφή (morphē) is the projected image of the object, or the shadow of the vase.
As Wikipedia notes,
The English word "form" may be used to translate two distinct concepts that concerned Plato—the outward "form" or appearance of something, and "Form" in a new, technical nature, that never
...assumes a form like that of any of the things which enter into her; ... But the forms which enter into and go out of her are the likenesses of real existences modelled after their patterns in a wonderful and inexplicable manner....
The objects that are seen, according to Plato, are not real, but literally mimic the real Forms.
So in terms of God, the form of God as it appears to us (where we are the prisoner in Plato's cave) is the μορφή (morphē). This term acknowledges that our ability to view God is imperfect, and we are not capable of truly seeing God fully and directly. In trinitarian thought, the incarnation of Jesus might be thought of in some contexts as μορφή (morphē) - as Jesus, that was how God was able to appear to us (which helps to put into context later discussions about the -ούσιος (ousia) "substance" and nature of God.)
Conversely, God's true form could be thought of as εἶδος (eidos). It holds the concept of God's true and actual form which we lack the ability and perspective to view properly due to our humanly limitations.
The two appear to be nearly synonymous, although in the New Testament, μορφῇ generally refers to actual, physical form, whereas εἶδος pertains more to appearance.
As an example of the differences between the two, one could say that the Docetists believed that Jesus had only the appearance - εἶδος - of being human, but not the actual form - μορφῇ - of a human; whereas the orthodox doctrine regarding Christ was that he had both human μορφῇ and εἶδος.
Three verses in the New Testament use this word, including the one you cited:
Mark 16:12 (RSV)
After this he appeared in another form to two of them, as they were walking into the country.
Philippians 2:5–6 (RSV)
Have this mind among yourselves, which is yours in Christ Jesus, who, though he was in the form of God, did not count equality with God a thing to be grasped
Philippians 2:7 (RSV)
but emptied himself, taking the form of a servant, being born in the likeness of men.
Five verses in the New Testament use this word, including the verse you cited:
Luke 3:22 (RSV)
and the Holy Spirit descended upon him in bodily form, as a dove, and a voice came from heaven, “Thou art my beloved Son; with thee I am well pleased.”
Luke 9:29 (RSV)
And as he was praying, the appearance of his countenance was altered, and his raiment became dazzling white.
John 5:37 (RSV)
And the Father who sent me has himself borne witness to me. His voice you have never heard, his form you have never seen;
2 Corinthians 5:7 (RSV)
for we walk by faith, not by sight.
1 Thessalonians 5:22 (RSV)
abstain from every form of evil.
εἶδος (G1491) emphasizes on the outward appearance.
μορφῇ (G3444) emphasizes on the inward structure.
Both means representational form but they are not synonyms. In fact, they have somewhat opposite meanings.
Classical Greek influenced NT Biblical Greek but they are not exactly the same language. Put a higher weight on the Biblical usages of these two words and less weight on the extra-Biblical writings.
The word form μορφῇ (morphé) is the Greek root for the words metamorphosis and morphing. It is unfortunate that the English word form emphasizes too much on the outward appearance. We are images of God. We are not morphés of God. The morphé of God is the form and content of God. The Godhead morphs into a representational form for our perception and interaction conveniences.
εἶδος and μορφή are synonyms but like all synonyms the semantic range of each overlap but are not identical:
εἶδος, ους, τό (Hom.+.—CRitter, Neue Unters. über Plato 1910, 228–320) ① the shape and structure of someth. as it appears to someone, form, outward appearance (X., Cyr. 1, 2, 1; Pla., Symp. 210b; Philostrat., Ep. 51; Gen 41:2–4; Ezk 1:26; Philo; Jos., Ant. 6, 296; TestSim 5:1; Mel., P. 47, 334 [Perler]) σωματικῷ εἴδει in bodily form Lk 3:22; cp. GEb 18, 36 (Just., D. 88, 4 ἐν εἴδει περιστερᾶς and oft.). τὸ εἶδος τοῦ προσώπου αὐτοῦ the appearance of his face Lk 9:29 (ApcEsdr 4:29 p. 29, 3 Tdf.). Of God (cp. Ex 24:17; Theoph. Ant. 1, 3 [p. 62, 8]) εἶδος αὐτοῦ (w. φωνή) J 5:37. Of the form of polytheists’ gods Dg 2:1. οὐκ ἔχειν εἶδος have no comeliness 1 Cl 16:3 (Is 53:2). τὸ πῦρ καμάρας εἶδος ποιῆσαν formed the shape of a vaulted room MPol 15:2. ② a variety of someth., kind (X., Pla. et al.; PTebt 58, 20f [111 B.C.]; PFay 34, 6; POxy 905, 6; Sir 23:16; 25:2; Philo; Jos., Ant. 10, 37 πᾶν εἶδος πονηρίας; Just., Tat., Ath. [here the ‘form’ of matter]) ἀπὸ παντὸς εἴδους πονηροῦ fr. every kind of evil 1 Th 5:22 (Unknown Sayings, p. 92 [money-changing?]) ③ the act of looking/seeing, seeing, sight (Num 12:8; Ps.-Clem., Hom. 17, 18 στόμα κατὰ στόμα, ἐν εἴδει καὶ οὐ διʼ ὁραμάτων καὶ ἐνυπνίων. So also the interpr. of 2 Cor 5:7 in Severian of Gabala [Pauluskomm. aus d. griech. Kirche ed. KStaab ’33, 291] and in Theodoret III 314 Noesselt) διὰ πίστεως, οὐ διὰ εἴδους by faith, not by sight 2 Cor 5:7 (the same contrast betw. πιστεύειν and ἰδεῖν [s. εἶδον 1a] also J 20:29).—PBrommer, ΕΙΔΟΣ et ΙΔΕΑ ’40. DELG and Frisk. B. 874. EDNT. M-M. TW.
Arndt, W., Danker, F. W., & Bauer, W. (2000). A Greek-English lexicon of the New Testament and other early Christian literature (3rd ed., p. 280). Chicago: University of Chicago Press.
μορφή, ῆς, ἡ (Hom.+) form, outward appearance, shape gener. of bodily form 1 Cl 39:3; ApcPt 4:13 (Job 4:16; ApcEsdr 4:14 p. 28, 16 Tdf.; SJCh 78, 13). Of the shape or form of statues (Jos., Vi. 65; Iren. 1, 8, 1 [Harv. I 67, 11]) Dg 2:3. Of appearances in visions, etc., similar to persons (Callisthenes [IV B.C.]: 124 Fgm. 13 p. 644, 32 Jac. [in Athen. 10, 75, 452b] Λιμὸς ἔχων γυναικὸς μορφήν; Diod S 3, 31, 4 ἐν μορφαῖς ἀνθρώπων; TestAbr A 16 p. 97, 11 [Stone p. 42] ἀρχαγγέλου μορφὴν περικείμενος; Jos., Ant. 5, 213 a messenger fr. heaven νεανίσκου μορφῇ): of God’s assembly, the church Hv 3, 10, 2; 9; 3, 11, 1; 3, 13, 1; Hs 9, 1, 1; of the angel of repentance ἡ μ. αὐτοῦ ἠλλοιώθη his appearance had changed m 12, 4, 1. Of Christ (ἐν μ. ἀνθρώπου TestBenj 10:7; Just., D. 61, 1; Tat. 2, 1; Hippol., Ref. 5, 16, 10. Cp. Did., Gen. 56, 18; of deities ἐν ἀνθρωπίνῃ μορφῇ: Iambl., Vi. Pyth. 6, 30; cp. Philo, Abr. 118) μορφὴν δούλου λαβών he took on the form of a slave=expression of servility Phil 2:7 (w. σχῆμα as Aristot., Cat. 10a, 11f, PA 640b, 30–36). This is in contrast to expression of divinity in the preëxistent Christ: ἐν μ. θεοῦ ὑπάρχων although he was in the form of God (cp. OGI 383, 40f: Antiochus’ body is the framework for his μ. or essential identity as a descendant of divinities; sim. human fragility [Phil 2:7] becomes the supporting framework for Christ’s servility and therefore of his κένωσις [on the appearance one projects cp. the epitaph EpigrAnat 17, ’91, 156, no. 3, 5–8]; on μορφὴ θεοῦ cp. Orig., C. Cels. 7, 66, 21; Pla., Rep. 2, 380d; 381bc; X., Mem. 4, 3, 13; Diog. L. 1, 10 the Egyptians say μὴ εἰδέναι τοῦ θεοῦ μορφήν; Philo, Leg. ad Gai. 80; 110; Jos., C. Ap. 2, 190; Just., A I, 9, 1; PGM 7, 563; 13, 272; 584.—Rtzst., Mysterienrel.3 357f) Phil 2:6. The risen Christ ἐφανερώθη ἐν ἑτέρᾳ μορφῇ appeared in a different form Mk 16:12 (of the transfiguration of Jesus: ἔδειξεν ἡμῖν τὴν ἔνδοξον μορφὴν ἑαυτοῦ Orig., C. Cels. 6, 68, 23). For lit. s. on ἁρπαγμός and κενόω 1b; RMartin, ET 70, ’59, 183f.—DSteenberg, The Case against the Synonymity of μορφή and εἰκών: JSNT 34, ’88, 77–86; GStroumsa, HTR 76, ’83, 269–88 (Semitic background).—DELG. Schmidt, Syn. IV 345–60. M-M. EDNT. TW. Spicq. Sv.
Arndt, W., Danker, F. W., & Bauer, W. (2000). A Greek-English lexicon of the New Testament and other early Christian literature (3rd ed., p. 659). Chicago: University of Chicago Press.
This article in Trench's NT Synonyms may be helpful...
