All the advances of the human race have been accelerated by freedom of expression and all the reverses in the human condition have been exacerbated by the lack of it.
The worst excesses by tyrants such as Hitler and Stalin were made possible by the suppression of dissent and abuse of the organs of free expression. Because Dr Josef Goebbels, Hitler's propaganda minister, dictated what might be published or broadcast in Nazi Germany in 1939, most Germans were led to believe that the German invasion of Poland was in fact a Polish invasion of Germany.
Those sceptical of Germans who knew nothing of the worst excesses of Nazism, such as the extermination camps, had never lived in a totalitarian environment deprived absolutely of free media and open dissent, and it was only after the publication of books such as Solzhenitsyn's The Gulag Archipelago that many in the disintegrating Soviet Union learned of the worst excesses of their own dictators.
Rumour alone is not enough for those in an absolute dictatorship to know the extent of their plight. The full truth can only emerge with publication and unfettered discussion within the normal restraints of agreed laws in a democracy. In short, people can know they are oppressed, but they cannot find out how oppressed they are unless they are able to determine how oppressed all their fellow citizens are as well, and how comprehensive that oppression is for all its victims.
The normal restraints of agreed laws in a democracy are reasonable restraints such as laws against defamation. This was recognised in Roman Law more than a thousand years ago through the maxim: "Who steals my name steals gold", because in the absence of this restraint any unscrupulous person may seriously damage another by publishing false witness without the victim having recourse to any remedy.
But beyond these reasonable restraints, freedom of expression should be unfettered and promoted in all societies committed to human progress because such progress depends on the first vital ingredient in any common endeavour - communication.
Whatever programme a government undertakes, whether to curb malaria or tuberculosis or to promote any other public campaign, its first requirement is to communicate the required information, and the best method of achieving such communication is by publication and broadcast.
That is the most practical sense in which free expression through free media is essential for progress, as well as vital for the promotion and preservation of itself, of media freedom itself, for the benefit of all. The medium of radio, the medium of print, the medium of television - these are the media central to the whole process of progress for the human race.
There is a price to pay because freedom of expression through free media includes, unfortunately, the right of bad media, of irresponsible journalism and of all sorts of sensational or tasteless excesses, within, however, the restraints of defamation law, and these baser manifestations of the craft of journalism are the heaviest portion of that price we pay for full freedom.
Yet on the whole, it is the freedom to publish bad journalism as well as good that generally yields the healthiest dividend in terms of public truth. Between the overstatement of many tabloids and the understatement of many broad-sheets enough of the basic truth seems to emerge over most public issues of any importance.
That is an important part of the reason why famines, massacres and genocides do not take place in democracies but only in autocracies without free and unfettered media.
Indeed, governmental or dictatorial excesses against the general populace are even possible in societies which allow only partial media freedoms, such as during the apartheid era in South Africa. In apartheid South Africa all radio, all television, and many of the newspapers were directly controlled by the governing National Party, and those few of our newspapers that were independent of such control were hemmed in by no fewer than 22 statutes governing what was permitted to be printed.
When you defied these you risked arrest, banning, closure of your newspaper or, at the least, prosecution under the above "laws" with stiff fines or imprisonment as possible penalties.
Yet some South African journalists did succeed in defying some of these laws effectively enough to help promote the mounting campaign that eventually succeeded in playing a part in the downfall of the apartheid system - but only after 38 years of misery under 316 apartheid laws aimed at the subjugation of the country's black majority.
The United Nations Declaration of Human Rights was a massive moral boost to all journalists in all countries who sought through their craft to oppose authoritarianism wherever it held sway. It reassured the embattled that there was a wider global aspiration to achieve basic human rights for all people elsewhere, and encouraged the belief that campaigners for freedom, far from being an isolated few, were in fact part of the many all over the world who shared the vision.
It may never be precisely measurable to what extent the Declaration helped achieve the human rights it enunciated 50 years ago. But what can be said in celebration of it is that it is surely no coincidence that the 50 years of the Declaration have seen the most massive advances in human rights in all the history of the human race. Fifty years ago most people in our world lived under some form of colonial exploitation or authoritarian or totalitarian subjection, and today most do not. And the Declaration was the rallying cry for the whole process.
Donald Woods was born in Transkei, South Africa, and was Editor of the Daily Dispatch newspaper there until his arrest and banning in 1977 for editorials accusing the apartheid regime of responsibility for the death of black leader, Steve Biko. He escaped to Britain with his family and was the inspiration for the 1988 film Cry Freedom. He is International Representative of the South African Institute for the Advancement of Journalism which trains journalists from all over Britain.