President Michael D Higgins has received an honorary doctorate from Indiana University where he studied in the 1960s.
The President also delivered the keynote address at two commencement ceremonies for 2,900 graduands attended by around 35,000 people in total.
President Higgins attended Indiana University, at the Bloomington campus, in 1966 and 1967 when he studied for a Masters in Sociology.
Today he was invited back to deliver the commencement address and was conferred with an honorary doctorate of Humane Letters.
Delivering his commencement address, the President described his time at the University as an "interesting" time of "discovery and achievement".
He advised the graduands to keep an open-mind and to be always "willing to challenge assumptions and to guard against intellectual hubris".
He warned that "pride in false certainties always brings dangerous consequences".
He urged them to constantly strive to try to improve the problems of the world that previous generations had failed to do.
He said the major challenges of the world deserved a global response.
He spoke about the inequality of the world, saying the "current distribution of live chances" around the world had to be "redressed" if the current inhabitants were to be able to pass it on, adding "we cannot be consumed in our own consumption"
He said he hoped the class of 2014 would be a generation who take the "first steps in a new ethical version of economics".
The 2,900 members of the Class of 2014 at Indiana University are made up of people from 75 countries and 49 of the 50 United States.
The oldest graduate is 70 years of age and the youngest is 19.
The ceremonies took place in the Indiana University Basketball stadium, home to the famous Hoosiers team, five times national champions.
President Higgins was also awarded a Distinguished Alumni Service Award here and fondly remembered his time studying there, at various buildings around the campus, including at the nearby bar, Nick's English Hut which had been his favourite social spot as a student.
Last night he was honoured at a special dinner hosted by the President of Indiana University, Michael Mc Robbie.
The former US Treasury Secretary Paul O'Neill was also honoured and joked about he felt pressure to give a good speech, given that he was sharing the stage with an Irish poet, but that he was honoured to do so.