If there is one thing above all that unites the millions of people across the Arab world who have been out on the streets protesting since the beginning of the year, it must surely be their demand to be able to choose their own rulers and live their lives free from fear.

And nowhere, I suspect, is that truer than in Libya, where the death yesterday of Muammar Gaddafi must increase substantially the chance that Libyans will now also have an opportunity to map out a better future for themselves and their nation.

Naturally enough, they have been celebrating the news of his demise. But we know, don't we, from Afghanistan, Iraq, Tunisia and Egypt, that the overthrow - even the death - of a hated autocrat doesn't necessarily spell the beginning of a bright new future.

It might do - you could even argue that it should do - but in the words of the old song, it ain't necessarily so.

Take Tunisia, for example, where this remarkable year of Arab upheaval and revolt began. This weekend, the people of Tunisia will get their first chance to exercise their newly-won freedom, by voting for a 217-seat Constituent Assembly. It will be, in all but name, a parliament, with a mandate to draw up a new constitution and appoint a transitional government.

Next month, Egypt will begin a similar process, under the baleful eye of the military, who have ruled the country since the overthrow of President Mubarak in February, and who - according to their many critics - have shown a marked reluctance to introduce the root-and-branch reforms that the Tahrir Square protesters were demanding.

In both countries, it is all too easy to find people who will tell you that they are deeply disappointed at how little has changed since those heady days in January and February. Economies are in a tail-spin, and jobs are as scarce as ever. Elections alone aren't likely to change that.

Perhaps that's one reason why in Tunisia only just over half of the people who are eligible to vote have registered to do so. A low turn-out on Sunday will do nothing to encourage the belief that a stable democracy is taking hold.

Another could be that, according to Erik Churchill writing this week in Foreign Policy, "many Tunisians have expressed doubts that the elections will be truly free and fair. Despite all evidence to the contrary, it is commonplace to hear arguments that the outcome has been predetermined by the West."

If the elections are fair - and the expectation is that they will be - it looks as if the Islamist party Ennahdha (Renaissance) will win the largest number of seats in the new assembly. And as soon as I write the word Islamist, I can almost hear the intake of breath.

So is Tunisia on its way to becoming another Iran? Not according to Ennahdha's leader, Rachid Ghannouchi, who wrote in The Guardian on Tuesday:

"Charges of theocratic tendencies continue to be levelled at us. However, we believe in a civic state, based on equality between all citizens, regardless of faith, gender or race. We believe that the right to political and social association and organisation should be guaranteed for every citizen. We believe in the independence of civil society from the state, within a free and fair democratic system based on the principle of protecting personal and public liberties and guaranteeing a balance between the state and society."

He also wrote: "We have long advocated democracy within the mainstream trend of political Islam, which we feel is the best system that protects against injustice and authoritarianism." And there are plenty of people, both in Tunisia and elsewhere, who wonder exactly what constitutes "the mainstream trend of political Islam".

All revolutions suffer from the curse of dashed expectations. But it's still less than 12 months since the end of the old order in both Tunisia and Egypt, and I can't believe that anyone seriously expected that decades of authoritarian rule would suddenly make way for the sunlit uplands of liberal democracy.

And as I've pointed out before, you need more than an election - even the most perfectly-run election - before you can boast of having introduced real democracy. An independent judiciary, equality before the law, religious and media freedoms - they are all essential ingredients as well.

On the other hand, you have to start somewhere. And that's what the people of Tunisia hope they'll be doing this weekend. We don't yet know when the people of Libya will get their chance to start mapping their new future.

We're going to be reporting from right across the Middle East and North Africa over the coming weeks: Paul Moss is already in Tunisia, and we'll be broadcasting the second of his reports from there tonight (Friday). Next week he'll be reporting from Morocco.

During November, we'll be reporting from Saudi Arabia and Iraq, and Ritula will be in Turkey to look at the region's fastest-emerging new power and ask whether it could be a model for other would-be Islamic democracies. I'll wrap up the season from Egypt early in the New Year.

I have a proposition for you this week: I'll give you one pound if you promise to give me £1,000 in return.

No? So why do you think Israel has agreed to release 1,000 Palestinian prisoners in return for the release by the Palestinian Islamist group Hamas of just one captured Israeli soldier?

The 25-year-old soldier's name is Gilad Shalit, and he's probably one of the best known men in Israel. He was snatched by Hamas fighters more than five years ago close to the border between Israel and the Gaza Strip - and he's been held, incommunicado, somewhere in Gaza ever since.

Within the coming days, he'll be freed, and there'll be mighty celebrations across the length and breadth of Israel.

His family, who have waged a relentless campaign to keep his name in the public eye and to put pressure on successive Israeli governments, will be ecstatic.

So will 1,000 Palestinian families, especially the relatives of the 315 Palestinians who were serving life terms in Israeli jails. (There are thought to be in total more than 10,000 Palestinians in Israeli prisons.)

But why did Israel agree to the lop-sided deal? There are several reasons: first, because it is an Israeli tradition to bring every lost soldier home, dead or alive. In the past, similar deals have been done to win the return of slain soldiers' bodies, or even of body parts.

Israel is a small country, with a conscript army. Israelis accept the reality of combat risk in the knowledge that the State will do anything, if the worst happens, to "bring the boys home".

Second, because Israel's prime minister, Benjamin Netanyahu, needed a victory. He's lost two important regional allies - Egypt's President Mubarak and Turkey under its ever-more assertive prime minister Recep Tayyip Erdogan - and was unable to prevent the Palestinian leader Mahmoud Abbas scoring a substantial propaganda coup at the United Nations last month with his appeal for Palestine to be recognised as a full State member of the UN.

So the deal for the release of Gilad Shalit is, in the words of Israeli political commentator Yossi Verter of Haaretz, "the most important deal of his [Netanyahu's] life ... he will forever be remembered as the man who brought back Gilad Shalit."

But the truth is that this deal has been on the table, more or less in its current form, for quite a while. What's changed is the regional political environment.

As Mr Netanyahu himself candidly put it: "With everything that is happening in Egypt and the region, I don't know if the future would have allowed us to get a better deal -- or any deal at all for that matter ... This is a window of opportunity that might have been missed."

As for Hamas, it needed to do something to show, after Mr Abbas's coup de théâtre at the UN, that it's still in the game. A thousand celebrating Palestinian families means thousands more Hamas supporters. The message is a simple one: Hamas's armed struggle gets 1,000 prisoners released, whereas the endless non-negotiations of Mr Abbas's Fatah get nothing.

Each side made some concessions to get this deal signed. Israel agreed that some, although not all, of the released Palestinian prisoners will be allowed to live in the West Bank or Gaza Strip (there was, apparently, endless haggling over individual names); Hamas agreed that some of the best-known prisoners, including the charismatic Marwan Barghouti, much touted as a potential future Palestinian leader, will stay behind bars.

As for what follows, who can tell? With both Netanyahu and Hamas strengthened, and with a shaky Gaza ceasefire in effect yet again, might they now be able to move forward on more substantive issues?

Optimists say it's possible. But in my experience, when it comes to the Middle East, optimists are usually disappointed.

I'm going to assume, for the sake of argument, that you are deeply concerned about what's happening in Syria.

I'm also going to assume, for the sake of the same argument, that when you mull over the options for international action to put pressure on the government of President Bashar al-Assad, you would much rather that such action was sanctioned by an appropriately worded UN security council resolution.

In other words, you thought - by and large - that the NATO-led military intervention in Libya was more acceptable than the US-led invasion of Iraq.

So here's my question: now that Russia and China have cast their vetoes to block a Security Council resolution on Syria - a resolution that had been much watered down in the hope of winning their acquiescence, if not their approval - what would you do?

Your choices are these: do nothing, on the grounds that you tried and failed; try again, with a different form of wording in an attempt to win over the Russians and Chinese; or say to hell with the UN, we'll go it alone, put together as broad a coalition as we can, and do what needs to be done to bring an end to the ghastly mess that Syria is becoming.

There is little doubt that the crisis is worsening. According to the UN, the death toll since the start of the anti-government uprising in March is now close to 3,000 - and many thousands more are believed to be in jail.

There are also growing indications that at least some of the anti-government protesters are now armed - in the cities of Hama and Homs there are now daily reports of clashes between security forces and armed opponents. From here to civil war is a short and slippery slope.

Why did the Russians and Chinese cast their vetoes? China did because Russia did - and because Chinese leaders are deeply suspicious of any foreign interference in what it regards as a country's domestic affairs. (If I say Tibet, you'll understand why.)

And Russia, according to the pro-government MP Sergei Markov whom I interviewed on Wednesday, won't endorse any UN resolution that might be seen as a step along a path which leads to a Libya-style intervention.

Remember, Moscow abstained in the vote on Security Council resolution 1973, which authorised the use of "all necessary means" to protect civilians and civilian-populated areas in Libya, short of foreign troops on the ground.

It's been regretting that abstention ever since. What's more, now that Prime Minister Vladimir Putin has made it clear that he expects soon to resume his former duties as President Vladimir Putin, there are already some signs that Moscow's foreign policy stance is beginning to harden, perhaps in anticipation of his return to the presidency.

The European Union and the United States have already imposed a long list of sanctions on Syria - and its powerful neighbour Turkey is talking of doing likewise.

But if President Assad was worried that he might face the full wrath of a toughly-worded Security Council resolution, he can rest easy: the threat has passed.

And those governments - in Washington, London and Paris - who worry about the threat to regional stability if Syria spirals into all-out civil war are left with a dilemma: how can they exert real pressure, and remain on the right side of international law, without the agreement of Russia and China? (By the way, South Africa, India, Brazil and Lebanon all abstained on the Syria resolution this week, so there's evidently still a lot of persuading to be done.)

Incidentally, a key factor in the Libya intervention was a request from the Arab League for a UN-approved no-fly zone. And there's no sign - at least so far - of any similar request being made regarding Syria.

In other words, stand by for many more weeks of diplomacy and arm-twisting before the UN tries again to come up with an acceptable formula for action.

Oh, and by the way, changing the subject entirely, if you enjoy radio drama, you may like to make a point of listening to Radio 4's Afternoon Play on Monday at 2.15pm. It's called "A Time to Dance" and one of the characters in it ... no, I really shouldn't spoil it for you. Let's just say you might recognise the voice.