If the Dutch lived in Ireland, Bismarck is supposed to have said, they would feed Europe; and if the Irish lived in Holland they would drown.
A hard saying no doubt, and certainly less true today than it may have seemed in the past. Irish beef now goes far and wide around the world to anyone who will pay for it. And it is only those who live by the Shannon who risk drowning.
But what is it in fact, what combination of geographical, social, cultural and political factors, that makes one country and not another, however transiently, what the world calls great?
Cut off from the major trading routes of the Mediterranean, independent but with a populous and powerful neighbour at its back, it was not inevitable that Portugal should seek an outlet abroad for its national energies. But should it choose to do so, geography had surely ordained in what direction it would look.
Leaving behind Cabo Sao Vicente on the south-west tip of Europe - o fim do mundo (the end of the world), it was said - successive Portuguese merchant explorers, Bartolomeu Dias, Vasco da Gama, Pedro Alvarez Cabral, Fernao Magalhaes (Magellan) set out in the 15th and 16th centuries to discover other worlds and their riches. The strategic aim, handsomely achieved, was to wrest control of the valuable eastern spice trade from the Mediterranean powers of Genoa and Venice. In the process many territories were "discovered" and colonised, Angola and Mozambique, Goa, Timor and Macau, which were to stay under Portuguese administration for hundreds of years, in most cases well beyond their commercial usefulness.
The Portuguese went west too, to Brazil, an accidental discovery of Cabral in 1500 - he was on his way to India - and were active commercially in Spain's American possessions, where they were eventually to become victims of their own success. In Mexico City and Lima Portuguese merchants operated general stores where everything was sold, "from diamonds to mere cumin, from the cheapest black slave to the costliest pearls". Many of these entrepreneurs however were, as rivals complained, "new Christians", which is to say Jews. This could not be allowed, and a rash of auto-dafes (executions) throughout the 1640s, instigated by the Inquisition, put a stop to their gallop.
After the exhilaration of the 16th century things seemed to go downhill. Edged out of the East by the Dutch, the Portuguese came increasingly to rely on Brazil. Too much indeed: by the early 19th century roles had been reversed, the foreign possession having become the power and the motherland the colony. Brazilian independence in 1822 was the logical conclusion.
In the 19th century French republican ideas began to make themselves felt, but not strongly enough as yet to shake the nation out of its by now profound slumbers. An emblematic figure is the novelist Eca de Queiroz's absurd comic creation Goncalo Mendes Ramires, the so-called "Nobleman of the Tower", a decaying aristocrat dedicated to the glorification of his ancient but in fact rather tawdry family history, while he himself prepares shamelessly to climb the greasy pole of factional parliamentary politics.
The reasons for the rise and decline of nations are obscure and complex, and perhaps best left to the experts. Certainly weakness in oneself plays a part, no less than strength in another or indeed factors beyond anyone's control. At any rate, the cycle continues: the great do not always stay great and, comfortingly, decline is reversible.
The republic finally arrived for Portugal, after a royal assassination or two, in 1910, but did not really "take". The country's intervention in the first World War, where it - and its African colonies - lost thousands of soldiers, was seen as a disaster, while in a country with no death penalty the habit of assassinating political leaders disconcertingly appeared to be catching on. A strong man was clearly needed, and in 1928 he arrived - Dr Antonio de Oliveira Salazar.
With Salazar's estado novo (new state), self-sufficiency and xenophobia became official ideology and the country settled down, "proudly alone" as the slogan had it, to over 40 years of poverty and cultural stagnation. Poverty for most but not for all: when the industrialist Alfredo da Silva died in 1942 his personal fortune was estimated as the sixth largest in the world. Salazar was an ardent imperialist for whom the world apart from his beloved colonies did not exist. In fact he left Portugal only once, to meet Franco at a Spanish border town. The impoverished masses were more adventurous, shipping out in their hundreds of thousands for Africa or the factories of France, Germany, Switzerland and Luxembourg. For those who remained life was grim: poverty, genteel or abject, was the rule outside the so-called "20 families", while the cultural commisars discouraged cosmopolitan (French) influence, promoting a literature that would be "truly Portuguese".
Salazar in due course gave way to Caetano, who in turn gave way himself in 1974 to the officers of the Armed Forces Movement. For a few years Portugal appeared to be flirting with the Cuban "solution", but thanks to a number of confirmed democrats, notably future prime minister and president Mario Soares, was spared that expensive cul-de-sac.
Instead, in 1986, it and Spain joined the EEC, much to the initial consternation of French and Italian farmers, who feared extinction; Europe, it was said, was the last continent the Portuguese discovered. Since then, under firm guidance from prime ministers Cavaco Silva and Guterres, the country has seen its per capita income rise from 54 per cent to 74 per cent of the EU average, a spectacular increase in less than half a generation. Behind the statistics is a reality any visitor can see, new roads, a building boom, the absence - in the towns at any rate - of obvious poverty and in Lisbon a beautiful metro system which puts Dublin to shame.
The Portuguese, it is said, are a patient people, and indeed they would need to be, given the amount of romantic guff written about them by foreigners. Guidebooks and popular histories seem to be stitched together on the basis of an astoundingly small and threadbare repertory of cliches - the fado song tradition and the Portuguese soul, saudade or wistful longing, the curious cults of Dr Sousa Martins and the lost king Sebastiao.
Like the Irish, another charming but hopeless people as their friends the English know, the Portuguese were persuaded their good days were in the past and it was not their destiny ever to sit down with the godless of Europe's "rich men's club" - of which they currently hold the presidency. Maybe so. And yet perhaps history will show that our characters can in fact be remade, not by solitary contemplation but through engagement, challenge and exchange, and our destinies reshaped, not by our stars but by ourselves.