Χαῖρε!
First of all, let me clarify: what we call “modern” pronunciation is not modern at all. It’s traditional. When the Greek scholars from Constantinople like Chrysoloras, Chalcocondyles, Argyropoulos, and Gazes (who all spoke ancient Greek conversationally might I add) fled the Turk to Western Europe in the 15th century, they used the only pronunciation that they knew, the one which had been handed down to them generation after generation. And that’s the one that was universally used in Europe during the Renaissance.
However, it didn’t take long for the Europeans to start suspecting that the Greek of their masters had been “corrupted.” First Aldus Manuntius, then Erasmus pointed out that Greek spelling was not phonetic, and they suggested that the true pronunciation should be “restored”. At that time, the estimate was that the “corruption” was relatively recent, and due to Turkish influence. The scholars elaborated many different arguments to prove their thesis, mostly by comparisons to Latin and by collecting anecdotes from ancient authors. By todays’ standards, most of these “proofs” would be laughed out of the room. For instance, diphthongs were considered to be more “manly,” whereas iotacism was “feeble” and “feminine.” The ancient sounds were “delicate” and “noble”, the modern ones “vicious”.
The most infamous example, of course, is Cratinus’ βῆ βῆ imitating the sound of bleating sheep, which is commonly taken to be “proof” that β = [ b] and η = [e] in Antiquity. But in English, don’t sheep say “bah, bah”? So by that logic, η = [a]. In Hebrew, by contrast, sheep say “ma, ma” and in Modern Greek they also say “me, me.” That would prove that β = [m]! The most that can be surmised from these transliterations is that sheep bleats sound roughly like a labial followed by a front vowel. But whether that labial is a plosive, a nasal, or a fricative or what the value of that vowel is we cannot deduce categorically. Different languages have different conventions. It is also interesting to note that the only reason this particular quote from Cratinus was preserved was because it was a linguistic curiosity. The usual transliteration of sheep sounds for the Greeks was βαὶ βαὶ. Cratinus’ quote was used as an illustration of a peculiarly Attic form.
In any case, for better or for worse the debate had begun, and partisans gathered on either side. In England, Chancellor Stephen Gardiner of Cambridge called the arguments in favour of the new pronunciation “an ape robed in purple” (simiam purpura indutam). He fully acknowledged that language may change over time. However, he held that a scholar ought to use the pronunciation consecrated by long tradition and the universal usage of the educated men of his age. In 1542, Gardiner passed an edict banning the new pronunciation in Cambridge, threatening any professor who used it with fines and expulsion from the university.
On the other side, the Erasmians continued developing new and ever stranger theories. For instance, in 1684, a certain German classicist called Heinrich Henning (Latinized as Henninius) wrote a treatise arguing that the ancients did not use accents, and that Greek should be pronounced according to the stress-rules of Latin (!).
Thankfully, however, since that time, linguistics, epigraphy, and papyrology have undoubtedly proved that the pronunciation we call “modern” is extremely ancient. Take a look at these Imperial-era mosaics (1st to 3rd centuries AD). The first is from Sparta:
https://pbs.twimg.com/media/C-fO4PxW0AAXwMR.jpg
The second is a mosaic from Zeugma in Asia Minor:
https://i.pinimg.com/originals/29/5e/5b/295e5bacccc39fc5c18887a2c6f5677f.jpg
You will notice that Ἀλκιβιάδης is spelled Ἀλκηβειάδης, Ἴκαρος is spelled Εἴκαρος, and Δαίδαλος is spelled Δέδαλος. So clearly, η = ι = ει and αι = ε.
This is how Greek was pronounced at the time of the Caesars. But how was it pronounced at the time of Pericles?
Sven-Tage Teodorsson, a Greek scholar for the University of Gothenberg, has done much research into the epigraphical corpora of ancient Attica. What he has found is that H alternates with I from the 6th century BC onwards, and EI frequently alternates with I from as early the 7th century BC. In fact, the latter should come as no surprise, given that the Romans always transliterated EI as I, e.g. Ἀτρείδης → Αtrides.
In the 1st c. BC, we have Dionysius of Halicarnassus transliterating the Latin names Titus Herminius and Aricini as Τῖτος Ἑρμήνιος and Ἀρικηνοί respectively, and Strabo transliterating Scipio as Σκηπίων.
What about the diphthong OI? According to Thucydides, when plague befell Athens during the Peloponnesian War, the people remembered an old oracle. However, they were unsure if the oracle had in fact predicted a λοιμός (plague) or a λιμός (famine):
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0199%3Abook%3D2%3Achapter%3D54
If οι was sounded as two distinct vowels, then there never would have been any confusion. The great antiquity of this monophthongal pronunciation of οι is further proved by Homer, who uses the Ionic word ξυνός, meaning κοινός (common). The fact that this variant existed means that οι was homophonous to υ.
What about the consonants? Well, in the Doric dialect, one often finds words with a B standing in place of the digamma F, thought to represent the sound [w]. For example ἀFέλιος (the sun) becomes ἀβέλιος . This is very strong evidence that B was a fricative, not a stop. The fact that Greek B was transliterated in Latin by B does not prove how the sound was pronounced in Greek. In Spanish, the most common realization of B is [β] but when non-Spanish speakers try to speak Spanish, they often resort to [ b]. German W is pronounced [v] but when German words containing W are borrowed into English (e.g. Volkswagen), they’re frequently pronounced with a [w] following the phonology of English.
Ancient Athenian inscriptions show alternations between the letters Φ and Θ, very understandable if they were fricatives, but quite unusual if they were stops:
https://www.jstor.org/stable/40265986?seq=1
In the Cratylus, Plato classifies the letters Φ, Ψ, Σ, and Z together as “breathy” (πνευματώδη), another indication that Φ was a fricative:
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0171%3Atext%3DCrat.%3Apage%3D427
One of the most popular arguments touted by the Erasmians in favour of the plosive value of Φ and the aspirates is an anecdote recounted by Quintilian about a Greek at the time of Cicero who was unable to pronounce the name Fundanius:
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A2007.01.0059%3Abook%3D1%3Achapter%3D4%3Asection%3D14
Quintilian uses this anecdote to comment on how Latin F is pronounced differently from Greek Φ. But all this proves is that the letters did not have their modern values, not what those values were. As it turns out, the usual reconstruction for Latin F at this time is not a labio-dental fricative [f] but a bilabial fricative [φ](pronounced as if you’re blowing the candles on a birthday cake). Now one of the features of voiceless bilabial fricatives when followed by a rounded vowel like o or the u in Fundanius is that they often become h. This is even attested in Old Latin, which has the form horctis besides the usual forctis (strong). Given this, it is very likely that Fundanius actually sounded like Hundanius, which is why the Greek could not pronounce it. If anything, this anecdote only proves that by Cicero’s time, Greek had already lost the rough breathing. Which brings me to my next point.
One main feature of the ancient pronunciation which undoubtedly has changed is the rough breathing [h], which has become silent. However, there are indications that its disappearance is quite ancient. In his Rhetoric to Alexander, Aristotle says the following:
“First, name everything by its proper name whatever you say, avoiding ambiguity…The following is an instance of avoiding ambiguities: some words for many things are the same, such as the ὀδός (smooth breathing) of doors and the ὁδός (rough breathing) on which one walks. In such instances you must always include the particular context. Our wording will be clear if we do these things, and we shall express two things through the earlier method.”
Rhetorica ad Alexandrum, Loeb 317 (Aristotle Problems, Volume II), pp. 563-564
When one abandons the traditional pronunciation, one actually misses out on a lot of puns and wordplay. Here are four examples:
1- Diogenes criticized the philosopher Aristippus for spending a lot of money on a prostitute, telling him: “Aristippus, you live with a common (κοινή) whore; either follow the Cynic way like me (κύνιζε) or stop.” If you say koiné and kunize, you miss the whole joke, but if you say kini and kinize, it’s crystal clear.
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A2008.01.0405%3Abook%3D13%3Achapter%3D55
2- In his 28th epigram, Callimachus rhymes ἔχει with ναίχι:
Λυσανίη, σὺ δὲ ναίχι καλός, καλός, ἀλλὰ πρὶν εἰπεῖν
τοῦτο σαφῶς, Ἠχώ φησί τις « ἄλλος ἔχει ».
"Lysanias, you are fair, yes fair, but before
this is said clearly, some Echo says, “he is another’s.”
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0226%3Atext%3Depigrams%3Apoem%3D28
3- In the Life of Aesop, there’s an episode where Aesop’s master Xanthus tells Aesop that he has invited guests over for a banquet, and that he wants him to stand behind the entrance and only let in the wise. Aesop does as he’s told, and every time someone knocks on the door, he asks, τί σείει ὁ κύων (what does the dog move?), which all the guests except one misunderstand for τίς σὺ εἶ ὧ κύων (who are you, you dog?) and, insulted, leave. The one wise guest who understands the question answers correctly, “the tail and the ears,” and is let in. The only way this episode could have taken place is if υ and ει were close in pronunciation:
https://archive.org/details/fabulaeromanense01eberuoft/page/272/mode/2up
4- In his Peace (ll.922ff), Aristophanes employs a series of rhymes for comedic effect. Among them, he rhymes βοΐ (bull) with βοηθεῖν (to help), and ὑΐ (pig) with ὑηνία (swinishness):
Oἰκέτης
ἄγε δὴ τί νῷν ἐντευθενὶ ποιητέον;
Τρυγαῖος
τί δ’ ἄλλο γ’ ἢ ταύτην χύτραις ἱδρυτέον;
Xορός
χύτραισιν, ὥσπερ μεμφόμενον Ἑρμῄδιον;
Τρυγαῖος
τί δαὶ δοκεῖ; βούλεσθε λαρινῷ βοΐ;
Χορός
βοΐ; μηδαμῶς, ἵνα μὴ βοηθεῖν ποι δέῃ
Τρυγαῖος
ἀλλ’ ὑῒ παχείᾳ καὶ μεγάλῃ;
Χορός
μὴ μή.
Τρυγαῖος
τιή;
Χορός
ἵνα μὴ γένηται Θεογένους ὑηνία.
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0037%3Acard%3D922
The whole idea that the “modern” pronunciation is unfit to use because it creates homophony is simply ridiculous. Every living language has homophones. So Greek pronounces ἡμεῖς and ὑμεῖς the same. So what? Doesn’t modern English have there, their, and they’re, here and hear, where and wear, meet and meat, right and write, son and sun? Isn’t “you” both second person singular, and second person plural? I would add that the Hellenistic grammarians were fully aware of homophonous sounds (which they called ἀντίστοιχα) and used these to rhetorical effect to embellish their compositions.
As for being unsuitable because of the lack of long vowels, that is just a disingenuous claim. Those following the Erasmian method do not pronounce the long vowels consistently. There is nothing preventing someone who uses the modern pronunciation from pronouncing the long vowels when reciting poetry. That’s what the Byzantines did and their Greek poetry is eons ahead of what anyone is capable of composing now.
Another point worth stressing is simply the fact that if one is to follow the principles of the “restored” pronunciation consistently, one should employ a different pronunciation when reading works from different periods, e.g. Homer, Plato, Callimachus, Polybius, the New Testament, Cassius Dio, etc. which is extremely impractical to say the least.
Given all of this, I find the choice of modern pronunciation a no-brainer. It’s not only extremely close to the ancient pronunciation, but it can also serve as a standard for scholars to pronounce Greek in a consistent manner, as opposed to an idiosyncratic hodgepodge coloured by one’s native accent. And on that note, I end with a quote:
“Actual pronunciation…is not a matter of theory, but of praxis: real sound, not a description of sound. Often confusing the two, most classicists, I suspect, would claim that we know fairly accurately what sounds the Greek alphabet represented, yet no two of us would sound alike in reading a given passage of prose or poetry. Our students, if they are interested, have no consistent models to follow. As a result, the pronunciation of Ancient Greek today generally bears no relation to any language, living or dead; it is an embarrassment. The less said aloud, the better. After all, the printed text provides enough challenges as it is: grammar, substance, theme (all much easier to write about); who has class time to spend on pronunciation? Where’s the benefit?.. Reading silently is not so much the problem; it is unavoidable. Rather, it is reading aloud badly. But who can teach us to do it well? By themselves, books cannot. We need living models…”
Matthew Dillon, “The Erasmian Pronunciation of Ancient Greek: A New Perspective.” Classical World 94, no. 4 (2001), p.323
Ἔρρωσο