Hello. I was curious regarding the process by which men joined holy orders historically.
I am aware of the practice of oblates in medieval Western Europe, where parents would dedicate a child to the monasteries. Regarding the Orthodox world, I have a friend who is a member of their church who told me monks were meant to be elderly widowed priests, however, given that in 1721, Peter the Great's church reforms forbid any man younger than 50 from becoming a monk, seems to imply that it wasn't just elderly widowers joining the monasteries.
I had wondered who generally became priests in the pre-industrial Catholic world (I know in the Orthodox countries the priesthood was somewhat hereditary) and who became monks in both cultures. Was it mostly child-oblates? Old priests like my friend claimed? Or was it a means of social mobility for intellectually inclined members of the non-monied classes?
Thanks
I can try and answer your question at least regarding Catholic diocesan priests (i.e. those not belonging to a religious order, but to a specific diocese instead) for the early modern era, especially the roughly one and a half centuries between the Thirty Years' War and the Napoleonic era. The first thing I need to note in order to convey a sense of how the priesthood worked during that time was that there were a lot of priests. In 1671, the priest of Schwennenbach in the diocese of Augsburg wrote that there were more priests around than positions to fill them, and in 1723 Viennese authorities started worrying about the "exorbitant numbers of idle clergy" arriving in the city. While the demand for them had risen equally sharply, it was still simply not big enough to guarantee a stable prebend for each and every of them, leading to a significant number of "Mass-readers" - "priests-for-hire" if you will that made money by offering to read Mass for whoever wanted to pay them. In some areas they could rise to enormous numbers; in some Italian and Spanish cities up to a tenth of the entire population might have been clergy of some sort, the male and femal religious convents included.
Where did all those priests come from? Generally speaking: the city. A recent study on diocesan priests in the western reaches of 1762 Bavaria showed that more than three fifths of them hailed from cities and towns with more than 1,000 inhabitants - a marked difference from the general population structure of this time and region, where more than 80% of all people lived in decidedly rural circumstances. This is actually not too surprising, since generally speaking it would have been significantly more difficult for the children of rural peasants to receive the necessary basic education or scrape together the funds to pursue a priestly career. Almost all of the 189 diocesan priests observed in the study were commoners, with only three of them being of nobility (although their presence would become ever more common the higher up you advanced through ecclesiastical hierarchy, culminating in the cathedral chapters which in northern and central Germany barred not only all non-nobles from membership, but in turned even demanded of prospective members to prove that their noble ancestry dated back at least two, three or even four generations in all directions). This pattern of priests predominantly hailing from the cities also holds for almost all of Catholic Europe, although in contrast to e.g. Germany and France a significant minority of bishops in Spain and southern Italy were of non-noble birth, growing up in what we would today call bourgeois urban households instead.
The urban character of priests as a social cohort didn't necessarily mean that they were focussing as much on the cities in their work either. Although it is true that broadly speaking a prebend in the city was more attractive for most priests due to higher incomes and more opportunities for entertainment, at least in Bavaria rural regions were hardly "underserviced"; with a few exceptions, no peasant was more than an hour of walking away from the next priest, and by numbers about a quarter of the diocesan priests in the aforementioned study lived and worked in towns with more than 1,000 inhabitants, compared to roughly 18% of the overall population: a mismatch, but not an overly dramatic one. In other areas this could be much more disproportionate. In Rome, for example, there was unsurprisingly no shortage of clergy at all, while simultaneously the rural region immediately surrounding the cities didn't even have a functioning parish system at times. But generally speaking this was the exception and not the rule.
The social background of the lower-ranking clergy was generally speaking "middle class", if you will. While there was a not too small number of priests growing up in influential and powerful, yet non-noble upper class families, as well as (in certain regions, at least) a number of priests growing up in poorer families, the bulk of them seems to have come from the broad social stratum inbetween. There is a lot of research still to be done on that, however!
Aspiring priests were supposed to document that they had independent sources of income or enough personal wealth to not have to resort to "undignified" behaviour like begging or the aforementions "Mass-reading". In practice, this was commonly circumvented or outright ignored, however, keeping the path at least theoretically open for men from poorer backgrounds. The paths to priesthood were varied; while the Council of Trent in theory demanded that every diocese maintain a seminary dedicated for the education of the clergy, in practice they were introduced only slowly and often begrudgingly. In some parts of Italy, it took until well into the 19th century for seminaries to be erected in every diocese. Those who could afford it attended universities, even though the degree necessary for priesthood needn't necessarily be a theological one. In Germany and Belgium there were a lot of Jesuit-led schools dedicated to educating the clergy at low prices, which led to many or (by the mid-18th century) most priests receiving some sort of education and degree there. In southern Europe you could still observe "apprentice priests" for a long time, who would learn their craft directly from an older and more experienced priest. This became ever rarer as time went on, however.
One last thing I should mention: Today we generally expect that you need to feel some sort of vocation or calling to enter the priesthood. This was for the most part (and as far as we can tell) not the case for early modern diocesan priests, where their entering the priesthood seems to almost always have been a very pragmatic and economic decision often made by the parents for their children who, by becoming priests, had the opportunity to not only attain new sources of income but to rise in social status as well.
Sources:
tl;dr: The answer heavily depends on which area, period, [and which monastic order] you supposedly focus on in medieval Latin West - it is not so easy to generalize.
While more can always be said on the topic, I hope some of my previous posts (see below) might satisfy OP's curiosity at the moment:
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I suppose monks in early medieval West (sometimes oblates officially at least down to the 12th century) were generally recruited from higher social strata like nobles than local parish priests (sometimes drawn even from unfree status - see my first linked post) at least until about 1100 CE.
At that phase, Catholic church neither banned their local clergy to get married (the clerical celibacy would official been prescribed by the canon of the second Lateran Council in the 12th century) and in some cases the office of local clergy might also have been de facto inheritable as OP wrote above for the Eastern church, but it was almost not certainly "the norm" for aged local parish priest across medieval Latin West to enter the monastery due to this different social origins. Anyway, we neither have much sources on individual local priests in early medieval Latin West.
Or was it a means of social mobility for intellectually inclined members of the non-monied classes?
Pre-education before the ordination was also certainly one of few means for non-noble commoners in early medieval West to get educated, but it did probably not guarantee the future career path after their ordination to priesthood to climb the social ladder further, especially in Early Middle Ages.
Even in Later Middle Ages, while some aspirants made use of "benefice/ prebend" system of the ecclesiastical office as a kind of stipend for the university, many local priests, especially vicars, often "hired" on behalf of such rectors with titular benefice to conduct actual pastoral care in the parish, were drawn mainly from peasants, and often remain their original local community throughout their life (see my second linked post).