The French term raison d'état means, literally, "reason of state", what today is encapsulated in our concept of "the national interest". The existence of this concept is so firmly implanted in contemporary notions of both patriotism and resistance that it is strange to think that it was once a novelty. Yet, in the sixteenth and seventeenth centuries, raison d'état was the fashionable buzzword on the lips of courtiers from Rome to London, derided and praised in equal measure. It all started with the man who inspired a new term for Satan, Niccolo Machiavelli.
Before Machiavelli, writers on political philosophy had been generally agreed on the virtues and methods appropriate to nations and those who would make them great. Although the ideas were more rooted in classical Greek philosophy, they were identified mostly with Cicero, who had Romanized them and made them widely available in his handbook for rulers, On Moral Obligations. This was one of the first books to be printed in Christendom, and Erasmus had a pocket-sized edition created so the would-be virtuoso would never be caught short.
These ideas can be briefly summarized by saying that out of two actions, the expedient and the moral, the latter was always to be preferred, even at a risk to your life. Happily, Cicero even believed he had proved that expediency and morality were in fact always the same thing. Morality was encapsulated in four cardinal virtues: justice, wisdom, temperance, courage; to practice these was to live well. The virtues of justice and liberality were thought to be especially appriopriate to rulers, and hence came to be known as the 'princely virtues', those which befitted a wise and gracious ruler. In the Renaissance, humanists attempted to appropriate this classical tradition for Christianity, just as Cicero had done for the Romans, and More's Utopia is the most famous example of a work purporting to show the compatibility of pagan virtue and Christian religion.
Then in 1519, Niccolo Machiavelli landed a cannonball in European political thought, one which no subsequent writer could ignore. His crime was to tell things how they were by pointing out the hypocrisy of rulers who purported to rule in the name of virtue and religion, but in fact abided by neither. Focusing on a recurrent theme throughout political thought and taking it to its logical conclusion, he pointed out that as the state's highest good was to maintain itself, it often had to take an expedient course of action which was in fact contrary to religion and morality. The Prince was a handbook for princes which gave them refreshing licence: all that mattered was that they appeared to be moral, not actually being moral. In fact, they could hardly be expected to be moral in a world where everyone else had long ago abandoned, or never really adhered to, Christian morality.
How convienient! Yet Machiavelli's impact over the next one hundred years was mixed and contradictory. By his own advice, for a ruler to explicitly embrace Machiavellian methods (the term was used at the time) was to lessen his image and so damage his state. Courtiers and rulers began to meditate on what this primacy of expediency meant for them, and wrestled with their wracked consciences; for though they were like us all dissimulators to a man, it is no easier to admit this to oneself than to another. A suspected atheist and sinner Machiavelli may be, they thought, but his ideas cannot be ignored.
From this battle of wills emerged the concept of raison d'état, the reason of state. The trailblazers of the new concept were the French, the Dutch and the Italians, all at the time experiencing great civil strife. In France, the wars of religion turned father against son; for the Dutch, a Catholic Spanish occupation; and Italy suffered foreign domination due to the ineptitude of its own rulers. In a dog-eat-dog world of conflicting loyalties and crisis for states, a doctrine of expediency over morality seemed appropriate, if not downright appealing.
Nevertheless, writers on raison d'état usually made a distinction between 'good' and 'bad' reason of state, so not all activity was sanctioned. However, they differed over where the distinction lay. Some regarded bad actions as ones which were immoral, others those actions which served to increase the glory of the ruler and not the nation. The writers urged princes to pursue their state's 'interest', which was a metaphysical conception of the perfect actions which a state could take in a given situation, which the rulers needed to discern and follow obediently. They would be aided in discerning this by wisdom, which could be derived from experience and history, and by making sure their courtiers had no ulterior motives and were likewise concerned with the nation's interest.
This sort of thinking is more like twentieth century political science than older political philosophy, as it is concerned with studying situations and actions and deciding what to do, rather than abstract speculation. Turning to older examples, the reason of state theorists found a new favourite from the annals of old: Tacitus, historian of Rome. Focusing on the first six books of his Annals, in which the main protagonist is the Emperor Tiberius, numerous discourses were written on the lessons Tacitus could teach present-day Europeans. Even the young Thomas Hobbes got in on the act.
This new focus on interest and expediency divorced from morality provoked an interesting reaction from the citizens who were subject to such machinations. The old philosophy of Stoicism, which focuses on internal discipline and order to reach harmony with the world, was revitalized. A number of writers came to the conclusion that no form of government was better than any other, but that civil order in general was a good, and so they should just co-operate with whoever happened to be in power, finding personal fulfillment in a zone of inner peace. Their reaction to absolute monarchy was to curb their own passions rather than the power of the monarch.
By the time of the Peace of Westphalia (which ended the Thirty Years' War and brought a degree of peace to Europe unknown in several generations), reason of state theory had been pretty well hammered out and nothing new was left to be added. The genre had in fact provided dozens of books which said essentially the same thing, all trying to reconcile the allure of Machiavelli with common humanity and Christianity. A new and more honest way of thinking about the state had allowed writers and thinkers to address important issues in an open way, but had also justified horrendous abuses and injuries in Europe's long crisis from the Dutch Revolt to the Peace of Westphalia, especially ones based around religion. No-one could afford to ignore Machiavelli's legacy, but by becoming a punchbag he had contributed to a more honest and open internal debate in Western political thought.
For three famous and readily available examples of the reason of state genre, see Francesco Guicciardini, Dialogue on the Government of Florence, Justus Lipsius, Sixe Bookes of Politickes or Civil Doctrine and Giovanni Botero, The Reason of State.