At Carm. (Odes) 4.2.17–20 Horace's catalogue of Pindar's poetry reaches his victory odes:

The text, transmitted without variants in our manuscripts, means ‘(Pindar deserves the laurel wreath whether he writes bold dithyrambs or sings of gods and heroes) or tells of those escorted home as gods by the Elean palm-branch, whether boxer or horse, and bestows on them a gift more valuable than a hundred statues’. The two italicized expressions are more difficult than the commentators seem willing to admit. I discuss them separately.

(1) If we take caelestis as accusative, as do most commentators and as I have translated it above,Footnote ¹ it gives the wrong sense, for the victors are not divine, and Pindar never presents his laudandi as gods or even as heroes: see the taxonomy at Ol. 2.1–7 (imitated at Carm. 1.12.1–3) and Ol. 5.24–5. The unbridgeable distinction between gods and mortals and the limitations of the mortal condition are favourite themes of Pindar.Footnote ² Horace himself does not regard victors as divine either. When he says (Carm. 1.1.6) that some people are raised to godhead by the victor's palm (won by collecting Olympic dust and just missing the turning-post with their overheated chariot wheels), he means this in a subjective sense: such is their unbalanced enthusiasm that they feel like gods. Olympic victors, just like the other types he mentions in that poem (including the poet in lines 29–36), are irrationally attached to their pursuits. If accusative caelestis is what Horace wrote in the present passage, its sense would have to be similarly subjective. But the idea that Pindar celebrates victors who imagine they are gods is unwelcome here. We need an accusative that means not ‘divine’ but, for example, ‘glorious’ or ‘successful’. I will suggest one below after discussing the second problem.

(2) The text implies that Pindar celebrates the animals that figure in the victories he celebrates.Footnote ³ As a general rule this is false. He does, to be sure, mention Hieron's horse Pherenicus (Ol. 1.18, Pyth. 3.74, mentioned also in Bacchylides 5), but that is a unique case: no other prize-winning animal is named in the victory odes. Furthermore, it seems ridiculous to say that he confers on a horse a gift more valuable than a hundred statues: do horses crave to be immortalized in song or the plastics arts? The embarrassment is increased if we suppose that he brings horses home as gods (caelestis): raising a horse to godhead takes us into the realm of the absurd. We need, as parallel to ‘boxer’, not a horse but a horseman. We need to get rid of the horse and restore not his rider but his owner, since the victors in events involving horses seem always to have employed others as riders or drivers.

Disobligingly, equitemue will not scan, and in any case it is not the rider himself on whom Pindar confers his gift. An obvious and easily corruptible turn of phrase to restore the idea that one man wins fame as a boxer and another by means of his horse would be pugilemue equoue.Footnote ⁴ The corruption of equo to equum is easily explicable since scribes often corrupt a word into the case of its neighbour and are often thrown by inconcinnitas.Footnote ⁵ We need only find a word on which this phrase could depend.

I suggested earlier that in the place occupied by caelestis there once stood an adjective or participle in the accusative plural with the meaning ‘successful’ or ‘famous’. Read:

The best parallel for clarentis pugilemue, etc. is supplied by the next poem in the book, Carm. 4.3.3–4, illum non labor Isthmius clarabit pugilem. If it is objected that clareo is not used elsewhere by Horace and is not attested in any Augustan author, a similar objection applies to claro, which is used by Lucretius and Cicero before Horace and by Statius after him but only once in between, by Horace himself in Carm. 4.3.

But commentators justify the text of Carm. 4.2 by referring to Ars P. 83–5:

This passage seems to be making the same false claim, that epinician poets are in the habit of praising animals. What it ought to say is ‘The Muses gave the power to tell upon the lyre about the gods and the children of the gods, and about the victor in boxing and the winner in horse-racing, etc.’.

But that is precisely what it does say provided we interpret equum as genitive. According to Bo,Footnote ⁶ Horace uses as genitive plurals deum (Sat. 2.2.104, 2.6.65), diuum (Carm. 4.6.22, Sat. 1.3.117 and perhaps also Carm. 1.2.25), nummum (Epist. 2.2.33) and Boeotum (Epist. 2.1.244), so there is no reason why he could not have used equum as genitive. As far as I can tell, only two editions, those of Kiessling–Heinze and Brink ad loc. consider this possibility. They both reject it and give bad reasons for doing so. Kiessling–Heinze cite Carm. 4.2.17 (inconclusive, as we have seen) and also Theocritus 16.46. But the latter passage (note the καί) falls short, in my judgement, of proving that when an epinician poet wrote about a victory in a horse race the animal was the primary beneficiary. The same is true of the Plutarch passage (Quaest. conv. 639E) cited by Gow ad loc. Brink rejects genitive equum because of the parallel in Carm. 4.2.18 and also cites the balance of the present passage. The latter seems a subjective reason: there is nothing wrong with the balance of ‘victorious boxer and winner in horse-racing’, a perfectly acceptable line containing parallel expressions for victory (uictorem, primum) and contrasting expressions for field (pugilem, equum certamine). This passage does not prove that in Horace's view Pindar praised horses.

But all may not be quite well yet, for if this is what Horace wrote and what he meant, his meaning has escaped the majority of translators and commentators I have been able to consult.Footnote ⁷ The fact that the transmitted text could be interpreted in two different ways tells against it, for Horace values clarity and hates baffling his reader: see Ars P. 448–9, where he recommends that the author have his work read by a friend, part of whose task is to eliminate unclarity and ambiguity (parum claris lucem dare coget, arguet ambigue dictum).Footnote ⁸ It therefore seems unlikely that he would have looked with final approval on a passage so ambiguously written that even those who considered the possibility of taking equum as a genitive have rejected it. A version of the line that would exclude the accusative interpretation is et pugilem uictorem et equum certamine primos. This gives an alternation between singular and plural (uictorem, primos) that is to be seen occasionally in Horace (for example, Sat. 1.1.29 miles nautaeque). Here perhaps the variation has more point than usual, since Pindar celebrates more victors in horse or chariot-racing than in boxing. The corruption from plural to singular can be explained by either the desire to produce two parallel singulars or the failure to see that equum is genitive, a failure shared by the works cited in n. 7 above.