The Europe project can no longer be about a parliament sitting in Brussels deciding the definition of chocolate, according to the European Youth Parliament (EYP) which is meeting in Dublin.
Its president, Ms Aoife Carroll, said the EU must not be about the desires of one government, or the policies of another.
"Europe cannot and should not be defined by what Prime Minister Berlusconi says to Chancellor Schröder," she said.
Some 206 delegates from 25 countries have travelled to Ireland for the 43rd session of the EYP
Opening the session, the President, Mrs McAleese, said membership of the European Union had brought miraculous changes to Ireland.
"We now have a level of self-belief, a surging of cultural self-confidence that very few people could have foreseen back 30 years ago."
The President reminded the delegates that yesterday was the anniversary of the passing of the Nazi party's outlawing of all opposition parties.
That unleashed "a living hell, an absolute hell on earth," she said and showed the "dreadful consequences that happen when we get things wrong".
It highlighted the need for democracy and trust between countries.
"So never ever underestimate the value of what you are doing here," Mrs McAleese said.
"You are the dreamers and the doers of Europe and you are a very, very high accomplishing generation."
The European Youth Parliament which is open to students between 18 and 22 years, was founded in 1987.
In the coming days, the members will debate issues such as the US defence policy, human cloning, economic migration and the Northern Ireland peace process.
Resolutions that are passed by the EYP will then be presented to the European Parliament for further discussion.
