The former USA president used an address in South Africa marking 100 years since the birth of Nelson Mandela to directly challenge the world view of his successor and reject the populism he fears is poisoning political life.
"Just by standing on the stage honouring Nelson Mandela, Obama is delivering an eloquent rebuke to Trump", said John Stremlau, a professor of global relations at the University of the Witwatersrand in Johannesburg, who called the timing auspicious with the commitments that defined Mandela's life "under assault" in the United States and elsewhere.
However, he explained, it "shows a poverty in ambition to just want to take more and more", adding that there should be an emphasis on "how much you can give".
Ramaphosa was a close friend of the late revered leader.
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At least two people lost their lives Sunday in France during celebrations for the country's World Cup 2018 win over Croatia . Author and journalist India Knight added: "I love the Croatian president hugging them all in the rain.
"I think people who believe that Nelson Mandela hasn't done anything, I think they have issues with themselves".
- Ndileka Mandela, Nelson Mandela granddaughterGranddad was a simple man at heart, he just loved simple things and being with his people and being with his family.
Obama has often spoken of how much Mandela, a liberal leader with activist roots, influenced him.
But, Mr Obama added: "I can't find common ground if someone says climate change is not happening when nearly all the world's scientists say it is".
"Who needs free speech as long as the economy is going good?" he said, in the speech lasting nearly 90 minutes.
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"We now stand at a crossroads, a moment in time at which two very different visions of humanity's future compete", Obama declared in his Nelson Mandela Lecture.
Barack Obama did not name anyone in particular when he denounced "strongman politics" and "shameless leaders who, caught in a lie, just double down and lie some more", but his target was obvious.
His speech highlighted how Mandela, who was imprisoned for 27 years, became South Africa's first black president after fighting to end the country's racist system of apartheid. If you start (by) saying it is an elaborate hoax. where do we start?
"The world's most prosperous and successful societies, the ones with the highest living standards, the highest levels of satisfaction among their people, happen to be those which have most closely approximated the liberal progressive ideal that we talk about", Obama argued. "Look around", he said, during the event marking the 100th anniversary of the anti-apartheid revolutionary's birth.
"So if were truly to continue Madiba's long walk toward freedom, we're going to have to to work harder, we're going to have to be smarter". The lecture, in partnership with the Motsepe Foundation, comes a day before Nelson Mandela's birthday, known as Nelson Mandela International Day and is themed: "Renewing the Mandela legacy and promoting active citizenship in a changing world". After his release, Mandela went on to lead the ANC to victory in the first democratic elections in 1994.
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