These are questions that theologians have grappled with throughout church history. The matter really comes down to how we determine what is holy: in other words, what in this world is set apart for God. In the early centuries of Christianity, the church was forced to continually define itself as distinct from pagan society and this established a simple line of division: the church, its ministers, and even its physical property were holy and everything else wasn't. This thinking continued into the later Middle Ages, but by then it became extreme. There was the world and there was the church and the two were seen as completely different and always at odds. So distinct was the church from the world that a man could literally step over a fence or a line drawn on the ground and find himself stepping from the holy to the profane. The problem became, though, that the daily lives of men were not considered part of the holy. They were part of the secular world, separated from the church and sometimes even from God. Daily work and family, laughter with friends, even the wonders of nature were viewed by many church leaders as separate from more lofty 'heavenly things.'
Reformation leaders like Luther and Calvin, writing in the 1500s, knew that this was not what scripture taught. They instilled, instead, that God called men not just to offices in the church but to every kind of labor and trade. So in their thinking, the farmer was no less holy than the priest, the innkeeper no less ordained by God than the bishop. As Luther wrote, 'What seem to be secular works are actually the praise of God and represent an obedience which is well-pleasing to him.'
The Reformers also taught that while God did not want men to be worldly in character, he nevertheless called them to be active in the world in order to fulfill his will. . . . the Reformers taught that holiness was a matter of conformity to the image of Jesus, which a man ought to exercise as openly in the world as possible. In other words, the Christian shoekeeper or candle maker served his God while he plied his trade as Jesus would- with skill, with excellence, with morality, and with joy. This would do more good in the world than a thousand monks hidden away in monasteries, so the Reformers believed. As Luther expressed in his usual blunt fashion, done to the glory of God, even 'household chores are more to be valued than all the works of monks and nuns.'
The Reformers, then, pulled down the artificial distinction between the sacred and the secular and sent men into the world to serve God by using their skills and trades in his honor. This Protestant ethos of work found its way into the lives of the Guinnesses through the deeply reformed faith of the first Arthur Guinness and certain of his descendants. Many of them understood that brewing could be done as a holy offering, as a craft yielded in service of God. They did not see themselves as secular, but rather as called. They did not see themselves as apart from Christian ministry, but rather as in the Christian ministry of industry and trade. They did not think of their brewing work as a menial way to pay the bills, hoping that they might compensate for such worldliness by giving occasional service to the church. No, they had absorbed the great Reformation ideal that everything a man did was to be done for God and that his calling and his vocation were usually the same thing. They understood that this transformed workbenches into altars and the labor of man's hands into liturgies pleasing to God. . . .
A banker can be called and as pleasing to God as Billy Graham may be when he preaches. A brewer can serve a valuable role in the kingdom of God as a missionary, a priest, or a pope. This is the truth of Christianity and this, too, is a core truth of the Guinness story. It explains much of the Guinness spirit; much of their success and the good that they have chosen to do in the world."
The Search for God and Guinness, pp. 156-159