By Henri Astier
BBC News, Paris
It is not just France's chattering classes that are engaging in vigorous debate about the EU constitution.
People at the other end of the social ladder have been actively involved too.
Emmaus, a leading charity for the destitute, has been holding discussions about the proposed treaty ahead of Sunday's referendum.
The debate gets tense, until one of the group angrily walks out
In one debate a dozen people men and women - homeless people, asylum seekers, and poor workers - meet at an Emmaus shelter in Paris's impoverished 20th arrondissement.
"The European constitution should not be a matter for just politicians to discuss," says the moderator. "We should talk about it as well."
The people gathered around the clean, comfortable foyer do not need much prompting.
Participants show surprising interest in the referendum, given that most are immigrants and only four are allowed to vote in France.
Another remarkable aspect of the debate is the clear-cut nature of opinions expressed.
Only two of those taking part do not know what to make of the constitution - a much lower proportion than the 25-30% undecided in the French population at large.
Opinions are particularly strong on what EU integration means for Africa, where most of the foreigners staying at the shelter come from.
A man from Ivory Coast speaks out vehemently against the constitution.
"If Europe develops it will do so it will do so to the detriment of Africa," he says, adding that his continent might get "crushed" by a stronger Europe.
A West African woman agrees. "It is the world, not just Europe, that needs unifying," she says.
"Europeans want to be closer to each other, and exclude outsiders. As an African I want the 'No' vote to win."
Hadi Sall, a Malian immigrant who broadly supports the treaty, concedes that EU integration is "not necessarily good for Africa".
But, he adds, there is little danger of fortress Europe closing in on itself.
"Even if they build a wall three times as high as the Berlin Wall, immigrants will keep coming," Mr Sall says.
All about money
The guests at Emmaus are not solely interested in the impact of the vote on Africa, and debate the main question being discussed across France: does the constitution favour a free-market or a social Europe?
A young man wearing a bandana and sandals reflects the view - widespread among many of the left- that the document is dangerously pro-business and will lead to West European investors packing off to low-cost Eastern Europe.
"Companies will desert France," he predicts. "This is a purely economic constitution. It's all about money."
This idea is countered by another young man with an impeccably pressed shirt and the trenchant tone of an academic.
"People say the free market has been written into the constitution. This is utterly wrong," he says.
After giving an overview of the EU treaties of Maastricht, Amsterdam and Nice, the neatly dressed man expands on the reinforced law-making powers of the parliament under the proposed constitution.
"This is not an economic constitution, but a political framework," he concludes.
As is the case for many similar debates played out on French TV every day, neither side seems to be listening to the other, and the discussion turns into a series of harangues.
At which point Mr Sall tries to defuse tensions.
"Europe has an economic dimension - look at Airbus," he says.
Hadi Sall: France founded the EU so cannot turn its back on it
"But it also has a social dimension... In fact you can't have one without the other. You need to create wealth in order to redistribute it."
But this attempt at reconciliation fails.
After more sharp words from the man in the bandana, his learned opponent tries to crush him with science: "Your economics are a red herring. This is a political treaty, not a mere rehash of the 1951 Steel and Coal Community."
Angry at being patronised, the youth stalks off, and from then on the debate settles down.
Most participants appear to support the treaty. "It is important that the 'Yes' camp should win," says a soft-spoken, middle-aged Pole.
"It would be such a pity if it lost."
Mr Sall is convinced that this will not happen.
"France is a founding member of the EU, along with Germany, Italy and Benelux countries. That's what we learnt in Africa," he says.
"When you are the initiator of something, you cannot turn your back on it."
But it is unclear whether the majority has persuaded the undecided. At the end of the discussion the moderator asks one of the waverers if he has made up his mind.
"I now know that I would vote No," says the man.
More stories by Henri Astier on French opinion ahead of the referendum: