Why were eunuchs so common/valued in the Byzantine empire?

Hello! A definite thank-you to /u/caffarelli for sending up the eunuchologist Bat Signal. :) Eunuchs are indeed a huge part of Byzantine court life, and they definitely do seem pretty strange from a modern point of view. Their role in Byzantium, too, is pretty unusual -- the only analogue to their extensive presence in government and general elite society I can think of is the eunuchs of imperial China. I'll try to go through your questions in order, since the answers to both are pretty closely related; I don't think I'm assuming too much specialist knowledge, but then again I'm in the middle of reading for comprehensive exams, so my definition of "specialist knowledge" might be kind of out of whack.

1.) Where do Byzantine eunuchs come from?

This is probably the hardest question to answer, because we generally have very little evidence from eunuchs themselves on this kind of thing. Famous eunuchs' biographies don't usually pay much attention to their life before (or after) becoming famous: there are quite a few eunuchs (Eustathios Kymineianos, Leo Sakellarios) who we only know from a few scattered references in letters or histories, who don't act as major historical players over long periods of time, and so aside from knowing they existed, probably, we can't say much else about their lives. Even Narses shows up pretty abruptly, after he's been Justin's minister for most of his reign, when he must have already been fairly old, at least by pre-modern standards; I think Procopius mentions that he was Armenian, but as far as I remember he says nothing about Narses' life before the Reconquest starts. The Suda's entry on Narses is a good example of what I'm talking about: this is something like a tenth-century encyclopedia entry, but it's mostly concerned with his administrative abilities, with just the tiny note at the end explaining even when he lived.

That said, we can say a few things. The general scholarly consensus seems to be that up until the eighth or ninth century most eunuchs in Byzantium were of foreign origin, and were also usually slaves. Christians were really uncomfortable with the idea of castration (Matt. 19:12 notwithstanding), and the Romans had been no great fans of it either, but even by the time of Constantine eunuchs were pretty well ensconced in the structure of government. In Late Antiquity, castration was seen as a kind of necessary evil: sure, eunuchs are duplicitous and effeminate, but they're also what keeps the government running, letting the emperor worry about important things while they do most of the practical/dirty work. The best solution seemed therefore to use foreign eunuchs. Once they were brought to court, they would be completely dependent on the emperor; they would have no family ties, no social network (outside of maybe the other eunuchs), and they could be replaced relatively easily if they tried to rebel. A lot of famous eunuchs from Late Antiquity were also foreigners: I've mentioned Narses, but there's also Chrysaphius, Antiochus the praepositus, and even Samonas, as late as the ninth century. Then again, castration within the boundaries of the empire was being outlawed at least as late as Leo VI (886-912), so it's clear that not all eunuchs were coming from outside even in Late Antiquity. In general, however, eunuchs in this period were still thought of as a quintessentially foreign category; one that might have become more or less integrated into the Byzantine world view, but not really embraced by it.

Starting in around the ninth century though, this starts to change, at least somewhat. Though there were still undoubtedly a great deal of foreign eunuchs in Byzantium, more and more frequently we start to see eunuchs who seem to be native Byzantines. Constantine Barbaros (a former servant of Samonas) seems to have been related to the Phokas family, as were Constantine and Anastasios Gongyles and John the Orphanotrophos; one of the most famous Byzantine eunuchs, Basil Lekapenos, was the illegitimate son of Romanos I. Now, admittedly, all of these guys are relatively elite, so I'm not sure how well their situations might have applied to eunuchs at lower levels of society; I think there are examples of saints' lives that mention provincial families castrating at least one son in the hopes of his attaining high government employment, though I can't think of any precisely at the moment. In any case, by this period eunuchs seem to have become accepted enough within Byzantine society that castration was no longer associated strictly with foreigners and criminal punishment -- it became a kind of means for social advancement, a way of offering your child(ren) a better life. (It's also during this period that castration as punishment becomes much rarer than it had been in Late Antiquity; when it occurs, it's usually commented on quite strongly.)

The question of consent remains difficult to determine. In Late Antiquity, castration was probably mostly non-consensual, at least for slaves. Christian authors of this period will sometimes talk about the use of voluntary castration (performed after puberty) as a kind of birth control; most eunuchs of this period were not this kind of eunuch. Accidental/"accidental" castration is a common trope in hagiography (where we get the most "biographical" records of eunuchs' lives) -- castration was still technically illegal, except in cases of medical necessity (another commonly-cited excuse), but apparently there was a real danger of accidentally injuring the testicles by swaddling babies too tightly, and the general Solomon was known to have been a eunuch for this reason. In later Byzantium, maybe ninth to twelfth centuries, it's harder to say. Presumably the odds of attaining a cushy government job weren't enough to justify the danger of a non-consensual operation, though this may be a lot of modern wishful thinking. But then again, it might not be -- the so-called Defense of Eunuchs, written by a eleventh/twelfth-century archbishop, shows a child actively desiring castration as a way of preserving his chastity. Some scholars think this text was written mostly as satire, or at least that it wasn't meant to be taken seriously, but it was written as a gift to the author's beloved brother (who was himself a eunuch), so there might be at least some truth in it. There's also several accounts of "mystical" castration, in which a saint (tormented by lust) will dream of an angel or another saint, who touches his genitalia or actually dream-castrates him, and then he awakes relieved of the burden of lustful urges; in this context, castration is actually something desirable, precisely because it removes an obstacle on the path to God. There was certainly a lot of thought that castration was a kind of "get out of the struggle for chastity free" card, but it might also have been desirable for exactly that reason. The religious context, too, adds a level of meaning that's very hard for moderns (or at least me) to get at: eunuchs are very frequently associated with angels, who are of course sexless and perfectly chaste. If all human beings, even eunuchs, are theoretically equal before God, eunuchs may have had a significant advantage in the pursuit of sanctity that could not be replicated by others.

2.) Why are eunuchs so favored for court positions? What made them so suited for this kind of job?

Eunuchs in courtly contexts do typically have very high-profile responsibilities. A ninth-century list of offices and titles records a huge number of court offices, many of which are open to both eunuchs and bearded men. A few of these (domestic, quaestor, and eparch of Constantinople) were only available to bearded men, though this was not always strictly enforced. There were however a large number of posts which could only be held by eunuchs (see p. 120-9 for an exact overview). You're definitely right to point this out -- it's kind of bizarre. It's not entirely clear how the Byzantines understood castration to affect a person; I mean, it's definitely certain that they thought it did, but sometimes those effects are talked about as if they were innate, not the result of surgical operation. (No author I know of discusses whether these bad qualities have still been present if castration had not been performed.) But why do they trust eunuchs with these positions?

Kathryn Ringrose, one of the major modern scholars on Byzantine eunuchs, argues that service was the key feature of eunuchs' gender presentation. Her book on the subject is titled The Perfect Servant, and it's devoted to exploring how the idea of service constituted the entirety of eunuch identity from the ninth to twelfth centuries. There's no doubt that Byzantines certainly thought eunuchs were suited to administrative work; they're clever enough to be able to react to problems as they arise, but manageable enough not to be overtly threatening (at least most of the time). Whether or not "service" was the sole criterion by which eunuchs were defined/defined themselves is a different matter; even the social isolation Ringrose argues for isn't necessarily an absolute (Samonas, to use him as an example yet again, tried to escape imperial service to reunite with his family in the Levant). Yet the association of eunuchs with service is definitely clear: like I said, in Late Antiquity most eunuchs were probably in fact slaves or at least freedmen, and it seems likely that this sort-of stigma persisted even as the original conditions for it were increasingly no longer the case. (cont'd.)