Ennoblement is the conferring of nobility—the induction of an individual into the noble class. Depending on time and region, various laws have governed who could be ennobled and how. Typically, nobility was conferred on individuals who had assisted the sovereign. In some countries (e.g., France under the Ancien Regime), this degenerated into the buying of patents of nobility, whereby rich commoners (e.g., merchants) could purchase a title of nobility.
Medieval theorists of nobility relied on earlier classical concepts (Platonic, Aristotelian and Christian-Hellenistic) of what personal traits and virtues constitute grounds for ennoblement. In Plato's Republic, he provides for promotion and degradation of citizens according to a strict spiritual meritocracy. In the words of Will Durant, "If the ruler's son is a dolt he falls at the first shearing; if the boot-black's son is a man of ability the way is clear for him to become a guardian of the state" (Durant, The Story of Philosophy, 1961, p. 28). In medieval times, heraldic writers cited biblical examples to demonstrate that nobility is not just a matter of descent but of virtue: Shem, Ham and Japheth sprang from the same father, yet Ham was ignoble and King David rose from shepherd to become king through sheer faith and soldierly fortitude. Bartolus defined natural nobility by reference to Aristotle, who in his Politics explains how some are marked out for freedom by their virtues (and specifically by their capacity to rule), and are so distinguished from the mass of men whose talents fit them only for a servile role. Those free men whose virtues thus fit them to rule Bartolus defines as the natural nobility. With regard to natural nobility, Bartolus applauded Dante Alighieri's argument in his Convivio that nobility does not derive from ancient riches adorned with fine manners, but is the meed of individual virtue. Bartolus argues that the prince should strive to make his dominion a true mirror of God's own by advancing only those who are naturally noble (see Maurice Keen, Chivalry, p. 149). Geoffroi de Charny, the noted celebrant of knighthood, argued "God will mark out those who labor valorously, even though they come of little estate" (Livre de chevalrie, in Oeuvres de Froissart, ed. K. de Lettenhove I, pt. iii, 494, 495). Napoleon Bonaparte and Friedrich Nietzsche were later to continue the tradition of promoting a vision of aristocratic meritocracy, although no longer within (and opposed to) the Catholic-chivalric framework.
Polish ancient law recognized also the terms:
After the reforms of Tsar Peter the Great in the early 18th century, noblemen in Russia were obligated to serve as civil or military officials. Personal nobility was automatically conferred to all civil and military officials starting with the corresponding rank of Captain. Hereditary nobility was conferred for all officials with the rank of Colonel (Any given military post had an equivalent civil one, rank-wise). The system was later extended to merchants and industrialists that with a successful career managing a business of moderate size would achieve personal or hereditary nobility.