President Michael D Higgins has warned about politicians trying to divide people based on race, religion and nationality.
Mr Higgins told a conference on Brexit and the future of Europe that all the issues that will test the EU in the future are common to everyone on the planet - climate change, migration and jobs.
"In the absence of an adequate and inclusive discourse and emboldened by those who seek to mimic the language of the far-right for short-term electoral advantage, these political forces - exploiting and drawing on the despair, alienation and anomie of citizens - seek to divide us against one another on the grounds of ethnicity, religion and nationality," the President said.
"While not succeeding in recent electoral contests to achieve majorities in the short term, their gains represent a formidable challenge to any future social cohesion."
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In a wide-ranging address on the future of Europe, President Higgins called for a focus on hope rather than fear.
"Let us therefore in the European Union lift our gaze to encompass the needs of all humanity, all of their history, their possible futures, and let us do such with recognition of all of our cultural diversity," he said.
"After all the challenges which will test the European Union in this century - climate change, global migration, the future of work - are common to us all on our fragile and shared planet.
"Our best aspirations, our sustainable future, can only be met by restoring social cohesion and promoting social justice within our institutions here at home, within the institutions of the European Union, and within our global institutions.
"Our horizons must be limitless, for we, all of us, owe to each other an imprescriptible moral duty.
"We need a new mind for our times, a mind informed by hope rather than fear, not only for Europe but for humanity itself on our shared and vulnerable planet."
Mr Higgins told the conference to mark the opening of Dublin City University's Brexit Institute that the last 30 plus years had seen a trajectory towards increasing inequalities of income, wealth, power and opportunities across societies and countries.
Mr Higgins said it continues to be presented as some natural order of things.
He also praised French President Emmanuel Macron and said it was refreshing to see a leading politician outline a programme for Europe.
"I would like to agree with President Macron - in the strongest terms - that we are at a moment when we must recognise that the Union cannot, as in the past, be reconstructed from above, but can only, if it is to survive in this new century, be renewed and rebuilt from below," he said.
But Mr Higgins warned that a Franco-German agreement on the future of the EU will not be enough to answer the deep and sincerely held concerns over equality.
The conference was also addressed by Hilary Benn, chairman of the UK House of Commons Committee on Exiting the EU, and Herman Van Rompuy, President emeritus of the European Council.
Mr Benn called on the European Union to ask itself how it lost a valued member.
"The EU faces a choice now about its future," he said.
Mr Benn said he favoured a new multi-speed union.
He said: "But it will be for European citizens, the 'European Street' to decide, and in making that choice I hope the EU will, at some point, pause and quietly ask itself how it came to lose one of its most important member states."
On whether Britain could rejoin the EU, Mr Benn said: "In life, never say never.
"If we end up in the position with a decent deal but no voice then who knows, at some time in the years ahead people may say wouldn't it be better if we had a bit of a voice."
And on the future of the Irish border, the committee chairman said: "Staying in the customs union is the only answer to the question.
"We above all here, and in Northern Ireland and the rest of the UK, understand better than anybody else just how important it is to keep the border as it is now."
Minister for Foreign Affairs Simon Coveney told the conference it was time for the UK to detail its future with Europe.
"It is clear that the EU shares our desire to establish as close a partnership as possible with the UK," he said.
"But we need to know, unambiguously now, what kind of partnership the UK is seeking. It is time for the UK to provide clarity on what it wants, through confronting the hard choices it faces."
Mr Coveney insisted the UK government had given a guarantee that a hard border with Ireland would be avoided.
He also said the deal on future relations between the EU and UK must also protect key sectors of the Irish economy.
On the future of the European single market, the minister called for it to be expanded into services.
"Here in Ireland, we should be able to get cheaper mortgages and better insurance deals from European banks and insurance companies," he said.
"This would be good for Ireland, good for Europe and is already long overdue."