The Taoiseach strongly advocated the adoption of the Nice Treaty during the Dáil debate on the legislation paving the way for the October referendum.
Mr Ahern said the State had reached a crossroads, a turning point of enormous consequence for its people. "Within weeks, the sovereign people of this Republic will cast a vote that will set our course far into the future. The result is awaited across Europe, within and without the Union.
"It will set new possibilities or new limits for Ireland. It will form our national horizon. The choice we make, more than any other single action we take as a people in the next few years, will decide our standing in the world and decide whether Ireland succeeds and moves ahead in the right direction.
"So I come to Dáil Éireann today to say with all the conviction that I can muster that Ireland must vote Yes if we are to advance as a society, as an economy and as a free people."
The Dáil will vote on the 26th Amendment to the Constitution Bill today.
Mr Ahern said the EU had been a powerful engine of economic and social progress in Ireland. "Without aid from Europe, our phenomenal progress would have been unimaginable. An Ireland outside the new Europe would still be the same old Ireland of unemployment and emigration - with more and more of our people leaving an Ireland left behind."
He said those who had consistently campaigned against the European project were campaigning negatively again.
"But the Eurosceptics cannot escape history: the European Union has been good for Ireland, and our place in it has played a vital part in lifting our standards of living and our quality of life. Since joining the EU, we have been able to attract unprecedented foreign investment. We have been able to create jobs and build prosperity in large part because we have served as a gateway to Europe for the English-speaking world."
This could be demonstrated in very real terms. "The structural and cohesion funds have been a driving force in our development through investments in roads, environmental services, public transport, education, training and the promotion of new industry.
"Between 1973 and 2001, Ireland received €15.5 billion from these funds, with over €800 million received in 2001 alone. That is an undisputed fact and the irrefutable reality of our membership in Europe.
"In agriculture, Ireland has received over €29 billion in market supports and direct payments - promoting our farming, keeping people on their land and sustaining our rural communities. CAP transfers from 1973 to 2001 amount to almost €32 billion and from now through 2006, we will receive billions more. Total transfers from Europe from 1973 to 2001 are some €45.6 billion ."
Mr Ahern added that, socially and politically, the State's horizons had broadened. "In particular, the relationship between Ireland and Britain has developed through our common membership of the European Union. This has been essential in our quest for peace on our own island."
He said he understood the concerns people had when the voted against the treaty last year. He knew that many people did not vote; many said they refrained from voting because they were not sure which side was right.
"Confusion reigned and I think the responsibility for much of that lies with all of us charged with leadership, both politicians and social partners, who have a duty to make the issues as clear as possible so the people of Ireland can make the most informed choice. The responsibility also lies with others who practice the politics of confusion as a political tactic.
"So when people ask why vote on this treaty again, I tell them there are many compelling reasons to do so. First, this is a decision of the utmost importance for Ireland, with serious implications for our long-term prosperity and place in the world.
"Second, the Government has acted to change the context in which the decision will be taken. The Seville Declarations confirmed that Nice poses no threat to our policy of military neutrality. The proposed amendment to the Constitution copperfastens this by making it clear that Ireland will never be committed to a common defence unless the Irish people agree otherwise in a referendum.
"Third, there has been, for the first time ever, a structured national debate on Europe in the National Forum, and the Government has put in place rigorous new arrangements to assist the Oireachtas in the more effective scrutiny of EU business.
"Fourth, and finally, our partners in Europe, present and future, have asked us to reconsider this question within the changed context.
For the applicant countries in particular, the outcome has profound implications."
