An ekphrasis is a verbal description of a visual object. The earliest one in European literature is the Homer’s description of the shield of Achilles in Iliad 18.

Ekphrases are full of different kinds of paradoxes: static scenes that are somehow full of motion; silent scenes that are somehow full of sound.

There is a temporal paradox, too: An ekphrasis describes a finished work of art in which any activity that is depicted in mediis rebus will never be finished. The first poet I am aware of to self-consciously draw attention to this last paradox is the anonymous author of The Shield of Herakles. The Shield is modeled on the aforementioned passage of Iliad 18, but its author shows his originality in reflecting on the work described in a way that Homer does not.

Here is how he describes the charioteers portrayed on the Herakles’s shield (Shield 305-13):

πὰρ δ’ αὐτοῖς ἱππῆες ἔχον πόνον, ἀμφὶ δ’ ἀέθλῳ    (305)
δῆριν ἔχον καὶ μόχθον· ἐυπλεκέων δ’ ἐπὶ δίφρων
ἡνίοχοι βεβαῶτες ἐφίεσαν ὠκέας ἵππους
ῥυτὰ χαλαίνοντες, τὰ δ’ ἐπικροτέοντα πέτοντο
ἅρματα κολλήεντ’, ἐπὶ δὲ πλῆμναι μέγ’ ἀύτευν.
οἳ μὲν ἄρ’ ἀίδιον εἶχον πόνον, οὐδέ ποτέ σφιν
νίκη ἐπηνύσθη, ἀλλ’ ἄκριτον εἶχον ἄεθλον.
τοῖσι δὲ καὶ προύκειτο μέγας τρίπος ἐντὸς ἀγῶνος,
χρύσειος, κλυτὰ ἔργα περίφρονος Ἡφαίστοιο.[1]

And in Barry Powell’s translation (266-73; his line numbers differ from the Greek text):

                                                                                                       Next to them
horsemen labored hard: They worked and contended for a prize.
Charioteers standing on plaited cars urged on their swift horses,
giving slack to their reins. The jointed cars flew on, rattling,
and the naves of the wheels shrieked. So they engaged in a labor
for which there was no end, and a victory never appeared for them,
and the prize remained unclaimed--a huge tripod set out
for them within the racecourse, made of gold, the famous work
of cunning Hephaistos.

Keats uses this conceit to great effect in his “Ode on a Grecian Urn.” I do not know whether he was thinking of the Shield, or even whether he knew the text (though I suspect he did); but he loved the paradox. First:

Fair youth, beneath the trees, thou canst not leave
       Thy song, nor ever can those trees be bare;
               Bold Lover, never, never canst thou kiss,
Though winning near the goal yet, do not grieve;
       She cannot fade, though thou hast not thy bliss,
               For ever wilt thou love, and she be fair!

Again:

Ah, happy, happy boughs! that cannot shed
         Your leaves, nor ever bid the Spring adieu;
And, happy melodist, unwearied,
         For ever piping songs for ever new;
More happy love! more happy, happy love!
         For ever warm and still to be enjoy'd,
                For ever panting, and for ever young;
All breathing human passion far above,
         That leaves a heart high-sorrowful and cloy'd,
                A burning forehead, and a parching tongue...

Again:

What little town by river or sea shore,
         Or mountain-built with peaceful citadel,
                Is emptied of this folk, this pious morn?
And, little town, thy streets for evermore
         Will silent be; and not a soul to tell
                Why thou art desolate, can e'er return.

Indeed, the paradox under consideration here features on all three central stanzas of Keats’s “Ode,” and the contrast between the timeless and the temporal features in the two framing stanzas at the poem’s beginning and end as well.

Keats’s “Ode” is one of the great poems in the English language; and its most essential structuring thought can be traced back to a little read poem in archaic Greece whose author we do not even know. In that respect, at least, we can say, “Thanks, Anon.”