Christendom refers to the Middle Ages where the Christian World was all powerful coupled with Pagan and Muslim influences in the world at that time. The term itself, Christendom can be understood by the number of nations throughout the world which were under the rule of the Catholic Church. The Byzantine Greek East and the Latin West were heavily influenced by Christendom during the Early Middle Ages. Plato’s ideal state all are linked with the soul which shows the influence that the Church had during this time on the people of the world. Here are some words from Plato’s ideal community:
... For a thousand years Europe was ruled by an order of guardians considerably like that which was visioned by our philosopher. During the Middle Ages it was customary to classify the population of Christendom into laboratores (workers), bellatores (soldiers), and oratores (clergy). The last group, though small in number, monopolized the instruments and opportunities of culture, and ruled with almost unlimited sway half of the most powerful continent on the globe. The clergy, like Plato's guardians, were placed in authority... by their talent as shown in ecclesiastical studies and administration, by their disposition to a life of meditation and simplicity, and ... by the influence of their relatives with the powers of state and church. In the latter half of the period in which they ruled [800 AD onwards], the clergy were as free from family cares as even Plato could desire [for such guardians]... [Clerical] Celibacy was part of the psychological structure of the power of the clergy; for on the one hand they were unimpeded by the narrowing egoism of the family, and on the other their apparent superiority to the call of the flesh added to the awe in which lay sinners held them.... In the latter half of the period in which they ruled, the clergy were as free from family cares as even Plato could desire (Durant, 2005).
In the late Middle Ages there was a rebirth of humanism that was influenced by priests, artists, writers, and political figures which saw a transformation to Christendom. The classical antiquity was discussed in Santayana’s work:
The enterprise of individuals or of small aristocratic bodies has meantime sown the world which we call civilised with some seeds and nuclei of order. There are scattered about a variety of churches, industries, academies, and governments. But the universal order once dreamt of and nominally almost established, the empire of universal peace, all-permeating rational art, and philosophical worship, is mentioned no more. An unformulated conception, the prerational ethics of private privilege and national unity, fills the background of men's minds. It represents feudal traditions rather than the tendency really involved in contemporary industry, science, or philanthropy. Those dark ages, from which our political practice is derived, had a political theory which we should do well to study; for their theory about a universal empire and a catholic church was in turn the echo of a former age of reason, when a few men conscious of ruling the world had for a moment sought to survey it as a whole and to rule it justly (Santayana, 1982).
References:
Durant, Will (2005).Story of Philosophy. New York: Simon & Schuster.
Santayana, George (1982).The Life of Reason. New York: Dover Publications.